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142a6fbb39
Both decoders treated every 3-component image as YCbCr, so RGB JPEGs (as written by cjpeg -rgb, and by some Adobe software) came out with wrong colours. Decide the colour space as libjpeg does: a JFIF marker means YCbCr; otherwise the transform flag of an Adobe APP14 marker decides (0 is RGB); otherwise component IDs 'R', 'G', 'B' mean RGB. Core loader: on colour targets R, G and B are stored in place in the row buffer and the YUV conversion is skipped. Greyscale builds now also decode G and B for RGB and combine them into luma per block, which needs every component to be one block per MCU; other RGB layouts are rejected there. Plugin: RGB needs one block per MCU for every component, otherwise it is rejected (colour targets fall back to jpegp). Colour builds convert the R, G and B planes to YCbCr in place after decoding, so display and greyscale view modes are unchanged; greyscale builds combine R, G and B into luma per block as the core does. Code size on the e200: core loader +351 bytes, plugin decoder +603 bytes. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Change-Id: Ib24a0b7690ca4c00b3ac01b2f511309efeac5975
77 lines
3.1 KiB
C
77 lines
3.1 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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*
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* JPEG image viewer
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* (This is a real mess if it has to be coded in one single C file)
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*
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* File scrolling addition (C) 2005 Alexander Spyridakis
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* Copyright (C) 2004 Jörg Hohensohn aka [IDC]Dragon
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* Heavily borrowed from the IJG implementation (C) Thomas G. Lane
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* Small & fast downscaling IDCT (C) 2002 by Guido Vollbeding JPEGclub.org
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#ifndef _JPEG_JPEG_DECODER_H
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#define _JPEG_JPEG_DECODER_H
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#include "jpeg_common.h"
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struct jpeg
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{
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int x_size, y_size; /* size of image (can be less than block boundary) */
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int x_phys, y_phys; /* physical size, block aligned */
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int x_mbl; /* x dimension of MBL */
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int y_mbl; /* y dimension of MBL */
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int blocks; /* blocks per MB */
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int restart_interval; /* number of MCUs between RSTm markers */
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int store_pos[4]; /* for Y block ordering */
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bool jfif; /* saw a JFIF APP0 marker */
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unsigned char adobe; /* Adobe APP14 transform flag + 1, 0 if none */
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bool rgb; /* the components are R, G, B rather than Y, Cb, Cr */
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unsigned char* p_entropy_data;
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unsigned char* p_entropy_end;
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int quanttable[4][QUANT_TABLE_LENGTH]; /* raw quantization tables 0-3 */
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int qt_idct[3][QUANT_TABLE_LENGTH]; /* per component, for IDCT */
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struct huffman_table hufftable[2]; /* Huffman tables */
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struct derived_tbl dc_derived_tbls[2]; /* Huffman-LUTs */
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struct derived_tbl ac_derived_tbls[2];
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struct frame_component frameheader[3]; /* Component descriptor */
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struct scan_component scanheader[3]; /* Huffman tables per component */
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int mcu_membership[6]; /* info per block */
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int subsample_x[3]; /* info per component */
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int subsample_y[3];
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};
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/* various helper functions */
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void default_huff_tbl(struct jpeg* p_jpeg);
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void build_lut(struct jpeg* p_jpeg);
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int process_markers(unsigned char* p_src, long size, struct jpeg* p_jpeg);
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/* the main decode function */
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#ifdef HAVE_LCD_COLOR
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int jpeg_decode(struct jpeg* p_jpeg, unsigned char* p_pixel[3],
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int downscale, void (*pf_progress)(int current, int total));
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#else
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int jpeg_decode(struct jpeg* p_jpeg, unsigned char* p_pixel[1], int downscale,
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void (*pf_progress)(int current, int total));
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#endif
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#endif /* _JPEG_JPEG_DECODER_H */
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