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Merged
merged 4 commits into from
Feb 5, 2025
Merged

Support JPEG compression #583

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0484ba2
stb_image_write: support jpeg comment
vmobilis Feb 2, 2025
8cfd226
Detect and save JPEG output format
vmobilis Feb 2, 2025
30c2726
Always zero-terminate JPEG comment
vmobilis Feb 2, 2025
daaf3d5
Comment block should be padded
vmobilis Feb 2, 2025
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37 changes: 31 additions & 6 deletions examples/cli/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1057,16 +1057,41 @@ int main(int argc, const char* argv[]) {
}
}

size_t last = params.output_path.find_last_of(".");
std::string dummy_name = last != std::string::npos ? params.output_path.substr(0, last) : params.output_path;
std::string dummy_name, ext, lc_ext;
bool is_jpg;
size_t last = params.output_path.find_last_of(".");
size_t last_path = std::min(params.output_path.find_last_of("/"),
params.output_path.find_last_of("\\"));
if (last != std::string::npos // filename has extension
&& (last_path == std::string::npos || last > last_path)) {
dummy_name = params.output_path.substr(0, last);
ext = lc_ext = params.output_path.substr(last);
std::transform(ext.begin(), ext.end(), lc_ext.begin(), ::tolower);
is_jpg = lc_ext == ".jpg" || lc_ext == ".jpeg" || lc_ext == ".jpe";
} else {
dummy_name = params.output_path;
ext = lc_ext = "";
is_jpg = false;
}
// appending ".png" to absent or unknown extension
if (!is_jpg && lc_ext != ".png") {
dummy_name += ext;
ext = ".png";
}
for (int i = 0; i < params.batch_count; i++) {
if (results[i].data == NULL) {
continue;
}
std::string final_image_path = i > 0 ? dummy_name + "_" + std::to_string(i + 1) + ".png" : dummy_name + ".png";
stbi_write_png(final_image_path.c_str(), results[i].width, results[i].height, results[i].channel,
results[i].data, 0, get_image_params(params, params.seed + i).c_str());
printf("save result image to '%s'\n", final_image_path.c_str());
std::string final_image_path = i > 0 ? dummy_name + "_" + std::to_string(i + 1) + ext : dummy_name + ext;
if(is_jpg) {
stbi_write_jpg(final_image_path.c_str(), results[i].width, results[i].height, results[i].channel,
results[i].data, 90, get_image_params(params, params.seed + i).c_str());
printf("save result JPEG image to '%s'\n", final_image_path.c_str());
} else {
stbi_write_png(final_image_path.c_str(), results[i].width, results[i].height, results[i].channel,
results[i].data, 0, get_image_params(params, params.seed + i).c_str());
printf("save result PNG image to '%s'\n", final_image_path.c_str());
}
free(results[i].data);
results[i].data = NULL;
}
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20 changes: 16 additions & 4 deletions thirdparty/stb_image_write.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1412,7 +1412,7 @@ static int stbiw__jpg_processDU(stbi__write_context *s, int *bitBuf, int *bitCnt
return DU[0];
}

static int stbi_write_jpg_core(stbi__write_context *s, int width, int height, int comp, const void* data, int quality) {
static int stbi_write_jpg_core(stbi__write_context *s, int width, int height, int comp, const void* data, int quality, const char* parameters) {
// Constants that don't pollute global namespace
static const unsigned char std_dc_luminance_nrcodes[] = {0,0,1,5,1,1,1,1,1,1,0,0,0,0,0,0,0};
static const unsigned char std_dc_luminance_values[] = {0,1,2,3,4,5,6,7,8,9,10,11};
Expand Down Expand Up @@ -1521,6 +1521,18 @@ static int stbi_write_jpg_core(stbi__write_context *s, int width, int height, in
s->func(s->context, (void*)YTable, sizeof(YTable));
stbiw__putc(s, 1);
s->func(s->context, UVTable, sizeof(UVTable));

// comment block with parameters of generation
if(parameters != NULL) {
stbiw__putc(s, 0xFF /* comnent */ );
stbiw__putc(s, 0xFE /* marker */ );
size_t param_length = std::min(2 + strlen("parameters") + 1 + strlen(parameters) + 1, (size_t) 0xFFFF);
stbiw__putc(s, param_length >> 8); // no need to mask, length < 65536
stbiw__putc(s, param_length & 0xFF);
s->func(s->context, (void*)"parameters", strlen("parameters") + 1); // std::string is zero-terminated
s->func(s->context, (void*)parameters, param_length - 2 - strlen("parameters") - 1);
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Might be missing a zero-termination for parameters with length above 65522 (0xFFFF - strlen("parameters") - 1 - 1)

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@vmobilis vmobilis Feb 2, 2025 •
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@idostyle, thanks for review.
JPEG comment block:
comment_marker { 0xFF, 0xFE /* comment marker */ }
comment_body {
  uint16be comment_body.length(),
  "comment" /* std::string terminates with 0 for compatibility with C strings */
}

Comment length can be 2..65535 bytes, according to https://www.w3.org/Graphics/JPEG/itu-t81.pdf, "Table B.8 – Comment segment parameter sizes and values".

     size_t param_length = std::min(2 + strlen("parameters") + 1 + strlen(parameters) + 1, (size_t) 0xFFFF);

// maker_length + len('parameters') + 0 + params.length() + 0,
// truncated to 65535 bytes, so comment can be 65535 - 2 - 10 - 1 - 1 = 65521 bytes.

     s->func(s->context, (void*)parameters, param_length - 2 - strlen("parameters") - 1);

// 65535 - 2 /* marker*/ - 10 - 1 /* 'parameters' + 0 */

Second 0, terminating params, is not substracted, therefore it will be written.

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@idostyle, I finally got it, you're right, despite that length of comment block is limited, it should always be terminated with 0, for safety. Fixed.

}

s->func(s->context, (void*)head1, sizeof(head1));
s->func(s->context, (void*)(std_dc_luminance_nrcodes+1), sizeof(std_dc_luminance_nrcodes)-1);
s->func(s->context, (void*)std_dc_luminance_values, sizeof(std_dc_luminance_values));
Expand Down Expand Up @@ -1625,16 +1637,16 @@ STBIWDEF int stbi_write_jpg_to_func(stbi_write_func *func, void *context, int x,
{
stbi__write_context s = { 0 };
stbi__start_write_callbacks(&s, func, context);
return stbi_write_jpg_core(&s, x, y, comp, (void *) data, quality);
return stbi_write_jpg_core(&s, x, y, comp, (void *) data, quality, NULL);
}


#ifndef STBI_WRITE_NO_STDIO
STBIWDEF int stbi_write_jpg(char const *filename, int x, int y, int comp, const void *data, int quality)
STBIWDEF int stbi_write_jpg(char const *filename, int x, int y, int comp, const void *data, int quality, const char* parameters)
{
stbi__write_context s = { 0 };
if (stbi__start_write_file(&s,filename)) {
int r = stbi_write_jpg_core(&s, x, y, comp, data, quality);
int r = stbi_write_jpg_core(&s, x, y, comp, data, quality, parameters);
stbi__end_write_file(&s);
return r;
} else
Expand Down