237 lines
8.3 KiB
C++
237 lines
8.3 KiB
C++
#include <emscripten/bind.h>
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#include <emscripten/val.h>
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#include <inttypes.h>
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#include <setjmp.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "config.h"
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#include "jpeglib.h"
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extern "C" {
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#include "cdjpeg.h"
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}
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using namespace emscripten;
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// MozJPEG doesn’t expose a numeric version, so I have to do some fun C macro
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// hackery to turn it into a string. More details here:
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// https://gcc.gnu.org/onlinedocs/cpp/Stringizing.html
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#define xstr(s) str(s)
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#define str(s) #s
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struct MozJpegOptions {
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int quality;
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bool baseline;
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bool arithmetic;
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bool progressive;
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bool optimize_coding;
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int smoothing;
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int color_space;
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int quant_table;
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bool trellis_multipass;
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bool trellis_opt_zero;
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bool trellis_opt_table;
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int trellis_loops;
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bool auto_subsample;
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int chroma_subsample;
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bool separate_chroma_quality;
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int chroma_quality;
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};
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int version() {
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char buffer[] = xstr(MOZJPEG_VERSION);
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int version = 0;
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int last_index = 0;
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for (int i = 0; i < strlen(buffer); i++) {
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if (buffer[i] == '.') {
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buffer[i] = '\0';
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version = version << 8 | atoi(&buffer[last_index]);
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buffer[i] = '.';
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last_index = i + 1;
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}
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}
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version = version << 8 | atoi(&buffer[last_index]);
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return version;
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}
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uint8_t* last_result;
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struct jpeg_compress_struct cinfo;
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val encode(std::string image_in, int image_width, int image_height, MozJpegOptions opts) {
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uint8_t* image_buffer = (uint8_t*)image_in.c_str();
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// The code below is basically the `write_JPEG_file` function from
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// https://github.com/mozilla/mozjpeg/blob/master/example.c
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// I just write to memory instead of a file.
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/* This struct contains the JPEG compression parameters and pointers to
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* working space (which is allocated as needed by the JPEG library).
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* It is possible to have several such structures, representing multiple
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* compression/decompression processes, in existence at once. We refer
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* to any one struct (and its associated working data) as a "JPEG object".
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*/
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/* This struct represents a JPEG error handler. It is declared separately
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* because applications often want to supply a specialized error handler
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* (see the second half of this file for an example). But here we just
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* take the easy way out and use the standard error handler, which will
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* print a message on stderr and call exit() if compression fails.
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* Note that this struct must live as long as the main JPEG parameter
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* struct, to avoid dangling-pointer problems.
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*/
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struct jpeg_error_mgr jerr;
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/* More stuff */
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JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */
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int row_stride; /* physical row width in image buffer */
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uint8_t* output;
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unsigned long size;
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/* Step 1: allocate and initialize JPEG compression object */
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/* We have to set up the error handler first, in case the initialization
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* step fails. (Unlikely, but it could happen if you are out of memory.)
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* This routine fills in the contents of struct jerr, and returns jerr's
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* address which we place into the link field in cinfo.
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*/
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cinfo.err = jpeg_std_error(&jerr);
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/* Now we can initialize the JPEG compression object. */
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jpeg_create_compress(&cinfo);
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/* Step 2: specify data destination (eg, a file) */
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/* Note: steps 2 and 3 can be done in either order. */
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/* Here we use the library-supplied code to send compressed data to a
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* stdio stream. You can also write your own code to do something else.
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* VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
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* requires it in order to write binary files.
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*/
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// if ((outfile = fopen(filename, "wb")) == NULL) {
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// fprintf(stderr, "can't open %s\n", filename);
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// exit(1);
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// }
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jpeg_mem_dest(&cinfo, &output, &size);
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/* Step 3: set parameters for compression */
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/* First we supply a description of the input image.
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* Four fields of the cinfo struct must be filled in:
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*/
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cinfo.image_width = image_width; /* image width and height, in pixels */
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cinfo.image_height = image_height;
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cinfo.input_components = 4; /* # of color components per pixel */
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cinfo.in_color_space = JCS_EXT_RGBA; /* colorspace of input image */
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/* Now use the library's routine to set default compression parameters.
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* (You must set at least cinfo.in_color_space before calling this,
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* since the defaults depend on the source color space.)
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*/
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jpeg_set_defaults(&cinfo);
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jpeg_set_colorspace(&cinfo, (J_COLOR_SPACE)opts.color_space);
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if (opts.quant_table != -1) {
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jpeg_c_set_int_param(&cinfo, JINT_BASE_QUANT_TBL_IDX, opts.quant_table);
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}
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cinfo.optimize_coding = opts.optimize_coding;
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if (opts.arithmetic) {
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cinfo.arith_code = TRUE;
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cinfo.optimize_coding = FALSE;
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}
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cinfo.smoothing_factor = opts.smoothing;
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jpeg_c_set_bool_param(&cinfo, JBOOLEAN_USE_SCANS_IN_TRELLIS, opts.trellis_multipass);
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jpeg_c_set_bool_param(&cinfo, JBOOLEAN_TRELLIS_EOB_OPT, opts.trellis_opt_zero);
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jpeg_c_set_bool_param(&cinfo, JBOOLEAN_TRELLIS_Q_OPT, opts.trellis_opt_table);
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jpeg_c_set_int_param(&cinfo, JINT_TRELLIS_NUM_LOOPS, opts.trellis_loops);
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// A little hacky to build a string for this, but it means we can use
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// set_quality_ratings which does some useful heuristic stuff.
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std::string quality_str = std::to_string(opts.quality);
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if (opts.separate_chroma_quality && opts.color_space == JCS_YCbCr) {
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quality_str += "," + std::to_string(opts.chroma_quality);
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}
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char const* pqual = quality_str.c_str();
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set_quality_ratings(&cinfo, (char*)pqual, opts.baseline);
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if (!opts.auto_subsample && opts.color_space == JCS_YCbCr) {
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cinfo.comp_info[0].h_samp_factor = opts.chroma_subsample;
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cinfo.comp_info[0].v_samp_factor = opts.chroma_subsample;
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}
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if (!opts.baseline && opts.progressive) {
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jpeg_simple_progression(&cinfo);
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} else {
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cinfo.num_scans = 0;
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cinfo.scan_info = NULL;
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}
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/* Step 4: Start compressor */
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/* TRUE ensures that we will write a complete interchange-JPEG file.
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* Pass TRUE unless you are very sure of what you're doing.
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*/
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jpeg_start_compress(&cinfo, TRUE);
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/* Step 5: while (scan lines remain to be written) */
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/* jpeg_write_scanlines(...); */
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/* Here we use the library's state variable cinfo.next_scanline as the
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* loop counter, so that we don't have to keep track ourselves.
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* To keep things simple, we pass one scanline per call; you can pass
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* more if you wish, though.
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*/
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row_stride = image_width * 4; /* JSAMPLEs per row in image_buffer */
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while (cinfo.next_scanline < cinfo.image_height) {
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/* jpeg_write_scanlines expects an array of pointers to scanlines.
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* Here the array is only one element long, but you could pass
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* more than one scanline at a time if that's more convenient.
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*/
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row_pointer[0] = &image_buffer[cinfo.next_scanline * row_stride];
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(void)jpeg_write_scanlines(&cinfo, row_pointer, 1);
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}
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/* Step 6: Finish compression */
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jpeg_finish_compress(&cinfo);
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/* Step 7: release JPEG compression object */
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last_result = output;
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/* And we're done! */
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return val(typed_memory_view(size, output));
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}
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void free_result() {
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/* This is an important step since it will release a good deal of memory. */
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jpeg_destroy_compress(&cinfo);
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}
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EMSCRIPTEN_BINDINGS(my_module) {
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value_object<MozJpegOptions>("MozJpegOptions")
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.field("quality", &MozJpegOptions::quality)
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.field("baseline", &MozJpegOptions::baseline)
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.field("arithmetic", &MozJpegOptions::arithmetic)
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.field("progressive", &MozJpegOptions::progressive)
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.field("optimize_coding", &MozJpegOptions::optimize_coding)
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.field("smoothing", &MozJpegOptions::smoothing)
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.field("color_space", &MozJpegOptions::color_space)
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.field("quant_table", &MozJpegOptions::quant_table)
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.field("trellis_multipass", &MozJpegOptions::trellis_multipass)
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.field("trellis_opt_zero", &MozJpegOptions::trellis_opt_zero)
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.field("trellis_opt_table", &MozJpegOptions::trellis_opt_table)
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.field("trellis_loops", &MozJpegOptions::trellis_loops)
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.field("chroma_subsample", &MozJpegOptions::chroma_subsample)
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.field("auto_subsample", &MozJpegOptions::auto_subsample)
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.field("separate_chroma_quality", &MozJpegOptions::separate_chroma_quality)
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.field("chroma_quality", &MozJpegOptions::chroma_quality);
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function("version", &version);
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function("encode", &encode);
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function("free_result", &free_result);
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}
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