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1058 lines
32 KiB
ObjectPascal
1058 lines
32 KiB
ObjectPascal
Unit JdpHuff;
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{ This file contains Huffman entropy decoding routines for progressive JPEG.
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Much of the complexity here has to do with supporting input suspension.
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If the data source module demands suspension, we want to be able to back
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up to the start of the current MCU. To do this, we copy state variables
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into local working storage, and update them back to the permanent
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storage only upon successful completion of an MCU. }
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{ Original: jdphuff.c ; Copyright (C) 1995-1997, Thomas G. Lane. }
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interface
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{$I jconfig.inc}
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uses
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jmorecfg,
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jinclude,
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jpeglib,
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jdeferr,
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jerror,
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jutils,
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jdhuff; { Declarations shared with jdhuff.c }
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{GLOBAL}
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procedure jinit_phuff_decoder (cinfo : j_decompress_ptr);
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implementation
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{ Expanded entropy decoder object for progressive Huffman decoding.
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The savable_state subrecord contains fields that change within an MCU,
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but must not be updated permanently until we complete the MCU. }
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type
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savable_state = record
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EOBRUN : uInt; { remaining EOBs in EOBRUN }
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last_dc_val : array[00..MAX_COMPS_IN_SCAN-1] of int;
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{ last DC coef for each component }
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end;
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type
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phuff_entropy_ptr = ^phuff_entropy_decoder;
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phuff_entropy_decoder = record
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pub : jpeg_entropy_decoder; { public fields }
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{ These fields are loaded into local variables at start of each MCU.
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In case of suspension, we exit WITHOUT updating them. }
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bitstate : bitread_perm_state; { Bit buffer at start of MCU }
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saved : savable_state; { Other state at start of MCU }
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{ These fields are NOT loaded into local working state. }
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restarts_to_go : uInt; { MCUs left in this restart interval }
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{ Pointers to derived tables (these workspaces have image lifespan) }
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derived_tbls : array[0..NUM_HUFF_TBLS-1] of d_derived_tbl_ptr;
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ac_derived_tbl : d_derived_tbl_ptr; { active table during an AC scan }
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end;
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{ Forward declarations }
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{METHODDEF}
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function decode_mcu_DC_first (cinfo : j_decompress_ptr;
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var MCU_data : array of JBLOCKROW) : boolean;
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far; forward;
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{METHODDEF}
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function decode_mcu_AC_first (cinfo : j_decompress_ptr;
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var MCU_data : array of JBLOCKROW) : boolean;
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far; forward;
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{METHODDEF}
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function decode_mcu_DC_refine (cinfo : j_decompress_ptr;
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var MCU_data : array of JBLOCKROW) : boolean;
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far; forward;
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{METHODDEF}
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function decode_mcu_AC_refine (cinfo : j_decompress_ptr;
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var MCU_data : array of JBLOCKROW) : boolean;
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far; forward;
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{ Initialize for a Huffman-compressed scan. }
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{METHODDEF}
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procedure start_pass_phuff_decoder (cinfo : j_decompress_ptr); far;
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var
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entropy : phuff_entropy_ptr;
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is_DC_band, bad : boolean;
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ci, coefi, tbl : int;
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coef_bit_ptr : coef_bits_ptr;
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compptr : jpeg_component_info_ptr;
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var
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cindex : int;
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expected : int;
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begin
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entropy := phuff_entropy_ptr (cinfo^.entropy);
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is_DC_band := (cinfo^.Ss = 0);
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{ Validate scan parameters }
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bad := FALSE;
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if (is_DC_band) then
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begin
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if (cinfo^.Se <> 0) then
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bad := TRUE;
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end
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else
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begin
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{ need not check Ss/Se < 0 since they came from unsigned bytes }
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if (cinfo^.Ss > cinfo^.Se) or (cinfo^.Se >= DCTSIZE2) then
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bad := TRUE;
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{ AC scans may have only one component }
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if (cinfo^.comps_in_scan <> 1) then
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bad := TRUE;
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end;
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if (cinfo^.Ah <> 0) then
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begin
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{ Successive approximation refinement scan: must have Al = Ah-1. }
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if (cinfo^.Al <> cinfo^.Ah-1) then
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bad := TRUE;
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end;
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if (cinfo^.Al > 13) then { need not check for < 0 }
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bad := TRUE;
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{ Arguably the maximum Al value should be less than 13 for 8-bit precision,
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but the spec doesn't say so, and we try to be liberal about what we
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accept. Note: large Al values could result in out-of-range DC
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coefficients during early scans, leading to bizarre displays due to
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overflows in the IDCT math. But we won't crash. }
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if (bad) then
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ERREXIT4(j_common_ptr(cinfo), JERR_BAD_PROGRESSION,
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cinfo^.Ss, cinfo^.Se, cinfo^.Ah, cinfo^.Al);
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{ Update progression status, and verify that scan order is legal.
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Note that inter-scan inconsistencies are treated as warnings
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not fatal errors ... not clear if this is right way to behave. }
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for ci := 0 to pred(cinfo^.comps_in_scan) do
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begin
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cindex := cinfo^.cur_comp_info[ci]^.component_index;
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coef_bit_ptr := coef_bits_ptr(@(cinfo^.coef_bits^[cindex])); {^[0] ???
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Nomssi }
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if (not is_DC_band) and (coef_bit_ptr^[0] < 0) then
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{ AC without prior DC scan }
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WARNMS2(j_common_ptr(cinfo), JWRN_BOGUS_PROGRESSION, cindex, 0);
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for coefi := cinfo^.Ss to cinfo^.Se do
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begin
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if (coef_bit_ptr^[coefi] < 0) then
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expected := 0
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else
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expected := coef_bit_ptr^[coefi];
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if (cinfo^.Ah <> expected) then
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WARNMS2(j_common_ptr(cinfo), JWRN_BOGUS_PROGRESSION, cindex, coefi);
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coef_bit_ptr^[coefi] := cinfo^.Al;
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end;
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end;
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{ Select MCU decoding routine }
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if (cinfo^.Ah = 0) then
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begin
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if (is_DC_band) then
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entropy^.pub.decode_mcu := decode_mcu_DC_first
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else
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entropy^.pub.decode_mcu := decode_mcu_AC_first;
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end
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else
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begin
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if (is_DC_band) then
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entropy^.pub.decode_mcu := decode_mcu_DC_refine
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else
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entropy^.pub.decode_mcu := decode_mcu_AC_refine;
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end;
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for ci := 0 to pred(cinfo^.comps_in_scan) do
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begin
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compptr := cinfo^.cur_comp_info[ci];
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{ Make sure requested tables are present, and compute derived tables.
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We may build same derived table more than once, but it's not expensive. }
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if (is_DC_band) then
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begin
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if (cinfo^.Ah = 0) then
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begin { DC refinement needs no table }
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tbl := compptr^.dc_tbl_no;
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jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
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entropy^.derived_tbls[tbl]);
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end;
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end
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else
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begin
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tbl := compptr^.ac_tbl_no;
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jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
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entropy^.derived_tbls[tbl]);
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{ remember the single active table }
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entropy^.ac_derived_tbl := entropy^.derived_tbls[tbl];
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end;
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{ Initialize DC predictions to 0 }
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entropy^.saved.last_dc_val[ci] := 0;
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end;
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{ Initialize bitread state variables }
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entropy^.bitstate.bits_left := 0;
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entropy^.bitstate.get_buffer := 0; { unnecessary, but keeps Purify quiet }
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entropy^.pub.insufficient_data := FALSE;
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{ Initialize private state variables }
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entropy^.saved.EOBRUN := 0;
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{ Initialize restart counter }
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entropy^.restarts_to_go := cinfo^.restart_interval;
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end;
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{ Figure F.12: extend sign bit.
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On some machines, a shift and add will be faster than a table lookup. }
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{$ifdef AVOID_TABLES}
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#define HUFF_EXTEND(x,s)
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((x) < (1shl((s)-1)) ? (x) + (((-1)shl(s)) + 1) : (x))
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{$else}
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{ #define HUFF_EXTEND(x,s)
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if (x) < extend_test[s] then
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(x) + extend_offset[s]
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else
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(x)}
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const
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extend_test : Array[0..16-1] of int = { entry n is 2**(n-1) }
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($0000, $0001, $0002, $0004, $0008, $0010, $0020, $0040,
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$0080, $0100, $0200, $0400, $0800, $1000, $2000, $4000);
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const
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extend_offset : array[0..16-1] of int = { entry n is (-1 shl n) + 1 }
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( 0, ((-1) shl 1) + 1, ((-1) shl 2) + 1, ((-1) shl 3) + 1, ((-1) shl 4) + 1,
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((-1) shl 5) + 1, ((-1) shl 6) + 1, ((-1) shl 7) + 1, ((-1) shl 8) + 1,
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((-1) shl 9) + 1, ((-1) shl 10) + 1, ((-1) shl 11) + 1, ((-1) shl 12) + 1,
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((-1) shl 13) + 1, ((-1) shl 14) + 1, ((-1) shl 15) + 1 );
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{$endif} { AVOID_TABLES }
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{ Check for a restart marker & resynchronize decoder.
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return:=s FALSE if must suspend. }
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{LOCAL}
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function process_restart (cinfo : j_decompress_ptr) : boolean;
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var
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entropy : phuff_entropy_ptr;
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ci : int;
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begin
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entropy := phuff_entropy_ptr (cinfo^.entropy);
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{ Throw away any unused bits remaining in bit buffer; }
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{ include any full bytes in next_marker's count of discarded bytes }
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Inc(cinfo^.marker^.discarded_bytes, entropy^.bitstate.bits_left div 8);
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entropy^.bitstate.bits_left := 0;
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{ Advance past the RSTn marker }
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if (not cinfo^.marker^.read_restart_marker (cinfo)) then
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begin
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process_restart := FALSE;
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exit;
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end;
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{ Re-initialize DC predictions to 0 }
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for ci := 0 to pred(cinfo^.comps_in_scan) do
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entropy^.saved.last_dc_val[ci] := 0;
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{ Re-init EOB run count, too }
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entropy^.saved.EOBRUN := 0;
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{ Reset restart counter }
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entropy^.restarts_to_go := cinfo^.restart_interval;
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{ Reset out-of-data flag, unless read_restart_marker left us smack up
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against a marker. In that case we will end up treating the next data
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segment as empty, and we can avoid producing bogus output pixels by
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leaving the flag set. }
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if (cinfo^.unread_marker = 0) then
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entropy^.pub.insufficient_data := FALSE;
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process_restart := TRUE;
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end;
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{ Huffman MCU decoding.
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Each of these routines decodes and returns one MCU's worth of
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Huffman-compressed coefficients.
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The coefficients are reordered from zigzag order into natural array order,
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but are not dequantized.
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The i'th block of the MCU is stored into the block pointed to by
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MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
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We return FALSE if data source requested suspension. In that case no
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changes have been made to permanent state. (Exception: some output
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coefficients may already have been assigned. This is harmless for
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spectral selection, since we'll just re-assign them on the next call.
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Successive approximation AC refinement has to be more careful, however.) }
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{ MCU decoding for DC initial scan (either spectral selection,
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or first pass of successive approximation). }
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{METHODDEF}
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function decode_mcu_DC_first (cinfo : j_decompress_ptr;
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var MCU_data : array of JBLOCKROW) : boolean;
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label
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label1;
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var
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entropy : phuff_entropy_ptr;
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Al : int;
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{register} s, r : int;
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blkn, ci : int;
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block : JBLOCK_PTR;
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{BITREAD_STATE_VARS;}
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get_buffer : bit_buf_type ; {register}
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bits_left : int; {register}
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br_state : bitread_working_state;
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state : savable_state;
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tbl : d_derived_tbl_ptr;
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compptr : jpeg_component_info_ptr;
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var
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nb, look : int; {register}
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begin
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entropy := phuff_entropy_ptr (cinfo^.entropy);
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Al := cinfo^.Al;
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{ Process restart marker if needed; may have to suspend }
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if (cinfo^.restart_interval <> 0) then
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begin
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if (entropy^.restarts_to_go = 0) then
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if (not process_restart(cinfo)) then
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begin
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decode_mcu_DC_first := FALSE;
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exit;
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end;
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end;
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{ If we've run out of data, just leave the MCU set to zeroes.
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This way, we return uniform gray for the remainder of the segment. }
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if not entropy^.pub.insufficient_data then
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begin
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{ Load up working state }
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{BITREAD_LOAD_STATE(cinfo,entropy^.bitstate);}
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br_state.cinfo := cinfo;
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br_state.next_input_byte := cinfo^.src^.next_input_byte;
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br_state.bytes_in_buffer := cinfo^.src^.bytes_in_buffer;
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get_buffer := entropy^.bitstate.get_buffer;
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bits_left := entropy^.bitstate.bits_left;
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{ASSIGN_STATE(state, entropy^.saved);}
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state := entropy^.saved;
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{ Outer loop handles each block in the MCU }
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for blkn := 0 to pred(cinfo^.blocks_in_MCU) do
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begin
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block := JBLOCK_PTR(MCU_data[blkn]);
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ci := cinfo^.MCU_membership[blkn];
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compptr := cinfo^.cur_comp_info[ci];
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tbl := entropy^.derived_tbls[compptr^.dc_tbl_no];
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{ Decode a single block's worth of coefficients }
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{ Section F.2.2.1: decode the DC coefficient difference }
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{HUFF_DECODE(s, br_state, tbl, return FALSE, label1);}
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if (bits_left < HUFF_LOOKAHEAD) then
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begin
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if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left, 0)) then
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begin
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decode_mcu_DC_first := FALSE;
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exit;
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end;
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get_buffer := br_state.get_buffer;
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bits_left := br_state.bits_left;
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if (bits_left < HUFF_LOOKAHEAD) then
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begin
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nb := 1;
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goto label1;
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end;
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end;
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{look := PEEK_BITS(HUFF_LOOKAHEAD);}
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look := int(get_buffer shr (bits_left - HUFF_LOOKAHEAD)) and
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pred(1 shl HUFF_LOOKAHEAD);
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nb := tbl^.look_nbits[look];
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if (nb <> 0) then
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begin
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{DROP_BITS(nb);}
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Dec(bits_left, nb);
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s := tbl^.look_sym[look];
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end
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else
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begin
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nb := HUFF_LOOKAHEAD+1;
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label1:
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s := jpeg_huff_decode(br_state,get_buffer,bits_left,tbl,nb);
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if (s < 0) then
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begin
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decode_mcu_DC_first := FALSE;
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exit;
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end;
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get_buffer := br_state.get_buffer;
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bits_left := br_state.bits_left;
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end;
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if (s <> 0) then
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begin
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{CHECK_BIT_BUFFER(br_state, s, return FALSE);}
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if (bits_left < s) then
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begin
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if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left,s)) then
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begin
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decode_mcu_DC_first := FALSE;
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exit;
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end;
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get_buffer := br_state.get_buffer;
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bits_left := br_state.bits_left;
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end;
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{r := GET_BITS(s);}
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Dec(bits_left, s);
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r := (int(get_buffer shr bits_left)) and ( pred(1 shl s) );
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{s := HUFF_EXTEND(r, s);}
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if (r < extend_test[s]) then
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s := r + extend_offset[s]
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else
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s := r;
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end;
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{ Convert DC difference to actual value, update last_dc_val }
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Inc(s, state.last_dc_val[ci]);
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state.last_dc_val[ci] := s;
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{ Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) }
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block^[0] := JCOEF (s shl Al);
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end;
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{ Completed MCU, so update state }
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{BITREAD_SAVE_STATE(cinfo,entropy^.bitstate);}
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cinfo^.src^.next_input_byte := br_state.next_input_byte;
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cinfo^.src^.bytes_in_buffer := br_state.bytes_in_buffer;
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entropy^.bitstate.get_buffer := get_buffer;
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entropy^.bitstate.bits_left := bits_left;
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{ASSIGN_STATE(entropy^.saved, state);}
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entropy^.saved := state;
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end;
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{ Account for restart interval (no-op if not using restarts) }
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Dec(entropy^.restarts_to_go);
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decode_mcu_DC_first := TRUE;
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end;
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{ MCU decoding for AC initial scan (either spectral selection,
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or first pass of successive approximation). }
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{METHODDEF}
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function decode_mcu_AC_first (cinfo : j_decompress_ptr;
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var MCU_data : array of JBLOCKROW) : boolean;
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label
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label2;
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var
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entropy : phuff_entropy_ptr;
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Se : int;
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Al : int;
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{register} s, k, r : int;
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EOBRUN : uInt;
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block : JBLOCK_PTR;
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{BITREAD_STATE_VARS;}
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get_buffer : bit_buf_type ; {register}
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bits_left : int; {register}
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br_state : bitread_working_state;
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tbl : d_derived_tbl_ptr;
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var
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nb, look : int; {register}
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begin
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entropy := phuff_entropy_ptr (cinfo^.entropy);
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Se := cinfo^.Se;
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Al := cinfo^.Al;
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{ Process restart marker if needed; may have to suspend }
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if (cinfo^.restart_interval <> 0) then
|
|
begin
|
|
if (entropy^.restarts_to_go = 0) then
|
|
if (not process_restart(cinfo)) then
|
|
begin
|
|
decode_mcu_AC_first := FALSE;
|
|
exit;
|
|
end;
|
|
end;
|
|
|
|
{ If we've run out of data, just leave the MCU set to zeroes.
|
|
This way, we return uniform gray for the remainder of the segment. }
|
|
if not entropy^.pub.insufficient_data then
|
|
begin
|
|
|
|
{ Load up working state.
|
|
We can avoid loading/saving bitread state if in an EOB run. }
|
|
|
|
EOBRUN := entropy^.saved.EOBRUN; { only part of saved state we care about }
|
|
|
|
{ There is always only one block per MCU }
|
|
|
|
if (EOBRUN > 0) then { if it's a band of zeroes... }
|
|
Dec(EOBRUN) { ...process it now (we do nothing) }
|
|
else
|
|
begin
|
|
{BITREAD_LOAD_STATE(cinfo,entropy^.bitstate);}
|
|
br_state.cinfo := cinfo;
|
|
br_state.next_input_byte := cinfo^.src^.next_input_byte;
|
|
br_state.bytes_in_buffer := cinfo^.src^.bytes_in_buffer;
|
|
get_buffer := entropy^.bitstate.get_buffer;
|
|
bits_left := entropy^.bitstate.bits_left;
|
|
|
|
block := JBLOCK_PTR(MCU_data[0]);
|
|
tbl := entropy^.ac_derived_tbl;
|
|
|
|
k := cinfo^.Ss;
|
|
while (k <= Se) do
|
|
begin
|
|
{HUFF_DECODE(s, br_state, tbl, return FALSE, label2);}
|
|
if (bits_left < HUFF_LOOKAHEAD) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left, 0)) then
|
|
begin
|
|
decode_mcu_AC_first := FALSE;
|
|
exit;
|
|
end;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
if (bits_left < HUFF_LOOKAHEAD) then
|
|
begin
|
|
nb := 1;
|
|
goto label2;
|
|
end;
|
|
end;
|
|
{look := PEEK_BITS(HUFF_LOOKAHEAD);}
|
|
look := int(get_buffer shr (bits_left - HUFF_LOOKAHEAD)) and
|
|
pred(1 shl HUFF_LOOKAHEAD);
|
|
|
|
nb := tbl^.look_nbits[look];
|
|
if (nb <> 0) then
|
|
begin
|
|
{DROP_BITS(nb);}
|
|
Dec(bits_left, nb);
|
|
|
|
s := tbl^.look_sym[look];
|
|
end
|
|
else
|
|
begin
|
|
nb := HUFF_LOOKAHEAD+1;
|
|
label2:
|
|
s := jpeg_huff_decode(br_state,get_buffer,bits_left,tbl,nb);
|
|
if (s < 0) then
|
|
begin
|
|
decode_mcu_AC_first := FALSE;
|
|
exit;
|
|
end;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
r := s shr 4;
|
|
s := s and 15;
|
|
if (s <> 0) then
|
|
begin
|
|
Inc(k, r);
|
|
{CHECK_BIT_BUFFER(br_state, s, return FALSE);}
|
|
if (bits_left < s) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left,s)) then
|
|
begin
|
|
decode_mcu_AC_first := FALSE;
|
|
exit;
|
|
end;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
{r := GET_BITS(s);}
|
|
Dec(bits_left, s);
|
|
r := (int(get_buffer shr bits_left)) and ( pred(1 shl s) );
|
|
|
|
{s := HUFF_EXTEND(r, s);}
|
|
if (r < extend_test[s]) then
|
|
s := r + extend_offset[s]
|
|
else
|
|
s := r;
|
|
|
|
{ Scale and output coefficient in natural (dezigzagged) order }
|
|
block^[jpeg_natural_order[k]] := JCOEF (s shl Al);
|
|
end
|
|
else
|
|
begin
|
|
if (r = 15) then
|
|
begin { ZRL }
|
|
Inc(k, 15); { skip 15 zeroes in band }
|
|
end
|
|
else
|
|
begin { EOBr, run length is 2^r + appended bits }
|
|
EOBRUN := 1 shl r;
|
|
if (r <> 0) then
|
|
begin { EOBr, r > 0 }
|
|
{CHECK_BIT_BUFFER(br_state, r, return FALSE);}
|
|
if (bits_left < r) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left,r)) then
|
|
begin
|
|
decode_mcu_AC_first := FALSE;
|
|
exit;
|
|
end;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
{r := GET_BITS(r);}
|
|
Dec(bits_left, r);
|
|
r := (int(get_buffer shr bits_left)) and ( pred(1 shl r) );
|
|
|
|
Inc(EOBRUN, r);
|
|
end;
|
|
Dec(EOBRUN); { this band is processed at this moment }
|
|
break; { force end-of-band }
|
|
end;
|
|
end;
|
|
Inc(k);
|
|
end;
|
|
|
|
{BITREAD_SAVE_STATE(cinfo,entropy^.bitstate);}
|
|
cinfo^.src^.next_input_byte := br_state.next_input_byte;
|
|
cinfo^.src^.bytes_in_buffer := br_state.bytes_in_buffer;
|
|
entropy^.bitstate.get_buffer := get_buffer;
|
|
entropy^.bitstate.bits_left := bits_left;
|
|
end;
|
|
|
|
{ Completed MCU, so update state }
|
|
entropy^.saved.EOBRUN := EOBRUN; { only part of saved state we care about }
|
|
end;
|
|
|
|
{ Account for restart interval (no-op if not using restarts) }
|
|
Dec(entropy^.restarts_to_go);
|
|
|
|
decode_mcu_AC_first := TRUE;
|
|
end;
|
|
|
|
|
|
{ MCU decoding for DC successive approximation refinement scan.
|
|
Note: we assume such scans can be multi-component, although the spec
|
|
is not very clear on the point. }
|
|
|
|
{METHODDEF}
|
|
function decode_mcu_DC_refine (cinfo : j_decompress_ptr;
|
|
var MCU_data : array of JBLOCKROW) : boolean;
|
|
|
|
var
|
|
entropy : phuff_entropy_ptr;
|
|
p1 : int; { 1 in the bit position being coded }
|
|
blkn : int;
|
|
block : JBLOCK_PTR;
|
|
{BITREAD_STATE_VARS;}
|
|
get_buffer : bit_buf_type ; {register}
|
|
bits_left : int; {register}
|
|
br_state : bitread_working_state;
|
|
begin
|
|
entropy := phuff_entropy_ptr (cinfo^.entropy);
|
|
p1 := 1 shl cinfo^.Al;
|
|
|
|
{ Process restart marker if needed; may have to suspend }
|
|
if (cinfo^.restart_interval <> 0) then
|
|
begin
|
|
if (entropy^.restarts_to_go = 0) then
|
|
if (not process_restart(cinfo)) then
|
|
begin
|
|
decode_mcu_DC_refine := FALSE;
|
|
exit;
|
|
end;
|
|
end;
|
|
|
|
{ Not worth the cycles to check insufficient_data here,
|
|
since we will not change the data anyway if we read zeroes. }
|
|
|
|
{ Load up working state }
|
|
{BITREAD_LOAD_STATE(cinfo,entropy^.bitstate);}
|
|
br_state.cinfo := cinfo;
|
|
br_state.next_input_byte := cinfo^.src^.next_input_byte;
|
|
br_state.bytes_in_buffer := cinfo^.src^.bytes_in_buffer;
|
|
get_buffer := entropy^.bitstate.get_buffer;
|
|
bits_left := entropy^.bitstate.bits_left;
|
|
|
|
{ Outer loop handles each block in the MCU }
|
|
|
|
for blkn := 0 to pred(cinfo^.blocks_in_MCU) do
|
|
begin
|
|
block := JBLOCK_PTR(MCU_data[blkn]);
|
|
|
|
{ Encoded data is simply the next bit of the two's-complement DC value }
|
|
{CHECK_BIT_BUFFER(br_state, 1, return FALSE);}
|
|
if (bits_left < 1) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left,1)) then
|
|
begin
|
|
decode_mcu_DC_refine := FALSE;
|
|
exit;
|
|
end;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
{if (GET_BITS(1)) then}
|
|
Dec(bits_left);
|
|
if (int(get_buffer shr bits_left)) and ( pred(1 shl 1) ) <> 0 then
|
|
block^[0] := block^[0] or p1;
|
|
{ Note: since we use OR, repeating the assignment later is safe }
|
|
end;
|
|
|
|
{ Completed MCU, so update state }
|
|
{BITREAD_SAVE_STATE(cinfo,entropy^.bitstate);}
|
|
cinfo^.src^.next_input_byte := br_state.next_input_byte;
|
|
cinfo^.src^.bytes_in_buffer := br_state.bytes_in_buffer;
|
|
entropy^.bitstate.get_buffer := get_buffer;
|
|
entropy^.bitstate.bits_left := bits_left;
|
|
|
|
{ Account for restart interval (no-op if not using restarts) }
|
|
Dec(entropy^.restarts_to_go);
|
|
|
|
decode_mcu_DC_refine := TRUE;
|
|
end;
|
|
|
|
|
|
{ MCU decoding for AC successive approximation refinement scan. }
|
|
|
|
{METHODDEF}
|
|
function decode_mcu_AC_refine (cinfo : j_decompress_ptr;
|
|
var MCU_data : array of JBLOCKROW) : boolean;
|
|
label
|
|
undoit, label3;
|
|
var
|
|
entropy : phuff_entropy_ptr;
|
|
Se : int;
|
|
p1 : int; { 1 in the bit position being coded }
|
|
m1 : int; { -1 in the bit position being coded }
|
|
{register} s, k, r : int;
|
|
EOBRUN : uInt;
|
|
block : JBLOCK_PTR;
|
|
thiscoef : JCOEF_PTR;
|
|
{BITREAD_STATE_VARS;}
|
|
get_buffer : bit_buf_type ; {register}
|
|
bits_left : int; {register}
|
|
br_state : bitread_working_state;
|
|
|
|
tbl : d_derived_tbl_ptr;
|
|
num_newnz : int;
|
|
newnz_pos : array[0..DCTSIZE2-1] of int;
|
|
var
|
|
pos : int;
|
|
var
|
|
nb, look : int; {register}
|
|
begin
|
|
entropy := phuff_entropy_ptr (cinfo^.entropy);
|
|
Se := cinfo^.Se;
|
|
p1 := 1 shl cinfo^.Al; { 1 in the bit position being coded }
|
|
m1 := (-1) shl cinfo^.Al; { -1 in the bit position being coded }
|
|
|
|
{ Process restart marker if needed; may have to suspend }
|
|
if (cinfo^.restart_interval <> 0) then
|
|
begin
|
|
if (entropy^.restarts_to_go = 0) then
|
|
if (not process_restart(cinfo)) then
|
|
begin
|
|
decode_mcu_AC_refine := FALSE;
|
|
exit;
|
|
end;
|
|
end;
|
|
|
|
{ If we've run out of data, don't modify the MCU. }
|
|
if not entropy^.pub.insufficient_data then
|
|
begin
|
|
|
|
{ Load up working state }
|
|
{BITREAD_LOAD_STATE(cinfo,entropy^.bitstate);}
|
|
br_state.cinfo := cinfo;
|
|
br_state.next_input_byte := cinfo^.src^.next_input_byte;
|
|
br_state.bytes_in_buffer := cinfo^.src^.bytes_in_buffer;
|
|
get_buffer := entropy^.bitstate.get_buffer;
|
|
bits_left := entropy^.bitstate.bits_left;
|
|
|
|
EOBRUN := entropy^.saved.EOBRUN; { only part of saved state we care about }
|
|
|
|
{ There is always only one block per MCU }
|
|
block := JBLOCK_PTR(MCU_data[0]);
|
|
tbl := entropy^.ac_derived_tbl;
|
|
|
|
{ If we are forced to suspend, we must undo the assignments to any newly
|
|
nonzero coefficients in the block, because otherwise we'd get confused
|
|
next time about which coefficients were already nonzero.
|
|
But we need not undo addition of bits to already-nonzero coefficients;
|
|
instead, we can test the current bit position to see if we already did it.}
|
|
|
|
num_newnz := 0;
|
|
|
|
{ initialize coefficient loop counter to start of band }
|
|
k := cinfo^.Ss;
|
|
|
|
if (EOBRUN = 0) then
|
|
begin
|
|
while (k <= Se) do
|
|
begin
|
|
{HUFF_DECODE(s, br_state, tbl, goto undoit, label3);}
|
|
if (bits_left < HUFF_LOOKAHEAD) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left, 0)) then
|
|
goto undoit;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
if (bits_left < HUFF_LOOKAHEAD) then
|
|
begin
|
|
nb := 1;
|
|
goto label3;
|
|
end;
|
|
end;
|
|
{look := PEEK_BITS(HUFF_LOOKAHEAD);}
|
|
look := int(get_buffer shr (bits_left - HUFF_LOOKAHEAD)) and
|
|
pred(1 shl HUFF_LOOKAHEAD);
|
|
|
|
nb := tbl^.look_nbits[look];
|
|
if (nb <> 0) then
|
|
begin
|
|
{DROP_BITS(nb);}
|
|
Dec(bits_left, nb);
|
|
|
|
s := tbl^.look_sym[look];
|
|
end
|
|
else
|
|
begin
|
|
nb := HUFF_LOOKAHEAD+1;
|
|
label3:
|
|
s := jpeg_huff_decode(br_state,get_buffer,bits_left,tbl,nb);
|
|
if (s < 0) then
|
|
goto undoit;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
r := s shr 4;
|
|
s := s and 15;
|
|
if (s <> 0) then
|
|
begin
|
|
if (s <> 1) then { size of new coef should always be 1 }
|
|
WARNMS(j_common_ptr(cinfo), JWRN_HUFF_BAD_CODE);
|
|
{CHECK_BIT_BUFFER(br_state, 1, goto undoit);}
|
|
if (bits_left < 1) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left,1)) then
|
|
goto undoit;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
{if (GET_BITS(1)) then}
|
|
Dec(bits_left);
|
|
if (int(get_buffer shr bits_left)) and ( pred(1 shl 1) )<>0 then
|
|
s := p1 { newly nonzero coef is positive }
|
|
else
|
|
s := m1; { newly nonzero coef is negative }
|
|
end
|
|
else
|
|
begin
|
|
if (r <> 15) then
|
|
begin
|
|
EOBRUN := 1 shl r; { EOBr, run length is 2^r + appended bits }
|
|
if (r <> 0) then
|
|
begin
|
|
{CHECK_BIT_BUFFER(br_state, r, goto undoit);}
|
|
if (bits_left < r) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left,r)) then
|
|
goto undoit;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
{r := GET_BITS(r);}
|
|
Dec(bits_left, r);
|
|
r := (int(get_buffer shr bits_left)) and ( pred(1 shl r) );
|
|
|
|
Inc(EOBRUN, r);
|
|
end;
|
|
break; { rest of block is handled by EOB logic }
|
|
end;
|
|
{ note s := 0 for processing ZRL }
|
|
end;
|
|
{ Advance over already-nonzero coefs and r still-zero coefs,
|
|
appending correction bits to the nonzeroes. A correction bit is 1
|
|
if the absolute value of the coefficient must be increased. }
|
|
|
|
repeat
|
|
thiscoef :=@(block^[jpeg_natural_order[k]]);
|
|
if (thiscoef^ <> 0) then
|
|
begin
|
|
{CHECK_BIT_BUFFER(br_state, 1, goto undoit);}
|
|
if (bits_left < 1) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left,1)) then
|
|
goto undoit;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
{if (GET_BITS(1)) then}
|
|
Dec(bits_left);
|
|
if (int(get_buffer shr bits_left)) and ( pred(1 shl 1) )<>0 then
|
|
begin
|
|
if ((thiscoef^ and p1) = 0) then
|
|
begin { do nothing if already set it }
|
|
if (thiscoef^ >= 0) then
|
|
Inc(thiscoef^, p1)
|
|
else
|
|
Inc(thiscoef^, m1);
|
|
end;
|
|
end;
|
|
end
|
|
else
|
|
begin
|
|
Dec(r);
|
|
if (r < 0) then
|
|
break; { reached target zero coefficient }
|
|
end;
|
|
Inc(k);
|
|
until (k > Se);
|
|
if (s <> 0) then
|
|
begin
|
|
pos := jpeg_natural_order[k];
|
|
{ Output newly nonzero coefficient }
|
|
block^[pos] := JCOEF (s);
|
|
{ Remember its position in case we have to suspend }
|
|
newnz_pos[num_newnz] := pos;
|
|
Inc(num_newnz);
|
|
end;
|
|
Inc(k);
|
|
end;
|
|
end;
|
|
|
|
if (EOBRUN > 0) then
|
|
begin
|
|
{ Scan any remaining coefficient positions after the end-of-band
|
|
(the last newly nonzero coefficient, if any). Append a correction
|
|
bit to each already-nonzero coefficient. A correction bit is 1
|
|
if the absolute value of the coefficient must be increased. }
|
|
|
|
while (k <= Se) do
|
|
begin
|
|
thiscoef := @(block^[jpeg_natural_order[k]]);
|
|
if (thiscoef^ <> 0) then
|
|
begin
|
|
{CHECK_BIT_BUFFER(br_state, 1, goto undoit);}
|
|
if (bits_left < 1) then
|
|
begin
|
|
if (not jpeg_fill_bit_buffer(br_state,get_buffer,bits_left,1)) then
|
|
goto undoit;
|
|
get_buffer := br_state.get_buffer;
|
|
bits_left := br_state.bits_left;
|
|
end;
|
|
|
|
{if (GET_BITS(1)) then}
|
|
Dec(bits_left);
|
|
if (int(get_buffer shr bits_left)) and ( pred(1 shl 1) )<>0 then
|
|
begin
|
|
if ((thiscoef^ and p1) = 0) then
|
|
begin { do nothing if already changed it }
|
|
if (thiscoef^ >= 0) then
|
|
Inc(thiscoef^, p1)
|
|
else
|
|
Inc(thiscoef^, m1);
|
|
end;
|
|
end;
|
|
end;
|
|
Inc(k);
|
|
end;
|
|
{ Count one block completed in EOB run }
|
|
Dec(EOBRUN);
|
|
end;
|
|
|
|
{ Completed MCU, so update state }
|
|
{BITREAD_SAVE_STATE(cinfo,entropy^.bitstate);}
|
|
cinfo^.src^.next_input_byte := br_state.next_input_byte;
|
|
cinfo^.src^.bytes_in_buffer := br_state.bytes_in_buffer;
|
|
entropy^.bitstate.get_buffer := get_buffer;
|
|
entropy^.bitstate.bits_left := bits_left;
|
|
|
|
entropy^.saved.EOBRUN := EOBRUN; { only part of saved state we care about }
|
|
end;
|
|
|
|
{ Account for restart interval (no-op if not using restarts) }
|
|
Dec(entropy^.restarts_to_go);
|
|
|
|
decode_mcu_AC_refine := TRUE;
|
|
exit;
|
|
|
|
undoit:
|
|
{ Re-zero any output coefficients that we made newly nonzero }
|
|
while (num_newnz > 0) do
|
|
begin
|
|
Dec(num_newnz);
|
|
block^[newnz_pos[num_newnz]] := 0;
|
|
end;
|
|
|
|
decode_mcu_AC_refine := FALSE;
|
|
end;
|
|
|
|
|
|
{ Module initialization routine for progressive Huffman entropy decoding. }
|
|
|
|
{GLOBAL}
|
|
procedure jinit_phuff_decoder (cinfo : j_decompress_ptr);
|
|
var
|
|
entropy : phuff_entropy_ptr;
|
|
coef_bit_ptr : int_ptr;
|
|
ci, i : int;
|
|
begin
|
|
entropy := phuff_entropy_ptr(
|
|
cinfo^.mem^.alloc_small (j_common_ptr (cinfo), JPOOL_IMAGE,
|
|
SIZEOF(phuff_entropy_decoder)) );
|
|
cinfo^.entropy := jpeg_entropy_decoder_ptr (entropy);
|
|
entropy^.pub.start_pass := start_pass_phuff_decoder;
|
|
|
|
{ Mark derived tables unallocated }
|
|
for i := 0 to pred(NUM_HUFF_TBLS) do
|
|
begin
|
|
entropy^.derived_tbls[i] := NIL;
|
|
end;
|
|
|
|
{ Create progression status table }
|
|
cinfo^.coef_bits := coef_bits_ptrrow (
|
|
cinfo^.mem^.alloc_small ( j_common_ptr (cinfo), JPOOL_IMAGE,
|
|
cinfo^.num_components*DCTSIZE2*SIZEOF(int)) );
|
|
coef_bit_ptr := @cinfo^.coef_bits^[0][0];
|
|
for ci := 0 to pred(cinfo^.num_components) do
|
|
for i := 0 to pred(DCTSIZE2) do
|
|
begin
|
|
coef_bit_ptr^ := -1;
|
|
Inc(coef_bit_ptr);
|
|
end;
|
|
end;
|
|
|
|
end. |