mirror of
https://github.com/openharmony/third_party_sane-airscan.git
synced 2026-06-30 21:17:55 -04:00
Alexander Pevzner
1fef40a18e
Some devices send image data in the different format, as requested (namely, Pantum M7100DN offers PNG, but sends JPEG instead) As result it causes scanning to fail, because PNG decoder can't recognize actually received JPEG image. The implemented solution is to dynamically detect image format, based on an image data signature. test-decode is also updated
79 lines
2.0 KiB
C
79 lines
2.0 KiB
C
/* AirScan (a.k.a. eSCL) backend for SANE
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*
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* Copyright (C) 2019 and up by Alexander Pevzner (pzz@apevzner.com)
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* See LICENSE for license terms and conditions
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*
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* Image decoding
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*/
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#include "airscan.h"
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#include <string.h>
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/* image_format_magic defines magic bytes for detection of
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* particular format
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*/
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typedef struct {
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ID_FORMAT format; /* Detected format */
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size_t off, len; /* Bytes offset and length within the image */
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uint8_t bytes[16]; /* Bytes to match */
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} image_format_magic;
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/* image_format_magic_tab contains magic bytes for known formats
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*/
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static image_format_magic
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image_format_magic_tab[] = {
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{ID_FORMAT_BMP, 0, 2, {'B', 'M'}},
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{ID_FORMAT_JPEG, 0, 2, {0xff, 0xd8}},
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{ID_FORMAT_PNG, 0, 8, {0x89, 'P', 'N', 'G', 0x0d, 0x0a, 0x1a, 0x0a}},
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{ID_FORMAT_TIFF, 0, 4, {'I', 'I', '*', '\0'}},
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{ID_FORMAT_TIFF, 0, 4, {'M', 'M', '\0', '*'}}
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};
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/* image_format_match matches image against the magic
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* If image matches, it returns ID_FORMAT, as defined by magic.
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* Otherwise, it returns ID_FORMAT_UNKNOWN
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*/
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static ID_FORMAT
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image_format_match (const image_format_magic *magic,
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const void *data, size_t size)
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{
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int cmp;
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if (magic->off + magic->len > size) {
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return ID_FORMAT_UNKNOWN;
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}
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cmp = memcmp(((const char*) data) + magic->off, magic->bytes, magic->len);
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if (cmp == 0) {
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return magic->format;
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}
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return ID_FORMAT_UNKNOWN;
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}
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/* Detect image format by image data
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*/
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ID_FORMAT
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image_format_detect (const void *data, size_t size)
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{
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size_t max = sizeof(image_format_magic_tab) /
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sizeof(image_format_magic_tab[0]);
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size_t i;
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for (i = 0; i < max; i ++) {
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const image_format_magic *magic = &image_format_magic_tab[i];
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ID_FORMAT format;
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format = image_format_match(magic, data, size);
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if (format != ID_FORMAT_UNKNOWN) {
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return format;
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}
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}
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return ID_FORMAT_UNKNOWN;
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}
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/* vim:ts=8:sw=4:et
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*/
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