write_jpeg.c

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//
// Copyright 2003 Sony Corporation 
//
// Permission to use, copy, modify, and redistribute this software for
// non-commercial use is hereby granted.
//
// This software is provided "as is" without warranty of any kind,
// either expressed or implied, including but not limited to the
// implied warranties of fitness for a particular purpose.
//

#include <stdio.h>
#include <stdlib.h>
#include <jpeglib.h>
#include "write_jpeg.h"

extern void jpeg_mem_dest(j_compress_ptr cinfo, JOCTET* buf, size_t bufsize);
extern int  jpeg_mem_size(j_compress_ptr cinfo);

int
write_jpeg_mem(unsigned char* YCbCr,
               int w, int h, int quality,
               unsigned char* dest, int destsize)
{
    JSAMPLE* image_buffer = (JSAMPLE*)YCbCr;
    int      image_width  = w;
    int      image_height = h;

    struct jpeg_compress_struct cinfo;
    struct jpeg_error_mgr jerr;

    JSAMPROW row_pointer[1];    /* pointer to JSAMPLE row[s] */
    int row_stride;             /* physical row width in image buffer */
    int jpegsize;

    cinfo.err = jpeg_std_error(&jerr);
    jpeg_create_compress(&cinfo);

    jpeg_mem_dest(&cinfo, dest, destsize);

    cinfo.image_width = image_width;
    cinfo.image_height = image_height;
    cinfo.input_components = 3;         /* # of color components per pixel */
    cinfo.in_color_space = JCS_YCbCr; /* colorspace of input image */

    jpeg_set_defaults(&cinfo);

    jpeg_set_quality(&cinfo,
                     quality, TRUE /* limit to baseline-JPEG values */);

    jpeg_start_compress(&cinfo, TRUE);

    row_stride = image_width * 3;       /* JSAMPLEs per row in image_buffer */

    while (cinfo.next_scanline < cinfo.image_height) {
        row_pointer[0] = & image_buffer[cinfo.next_scanline * row_stride];
        (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
    }

    jpeg_finish_compress(&cinfo);
    jpegsize = jpeg_mem_size(&cinfo);

    jpeg_destroy_compress(&cinfo);

    return jpegsize;
}

void
write_jpeg_file(unsigned char* YCbCr, int w, int h, int quality, FILE* outfile)
{
    JSAMPLE* image_buffer = (JSAMPLE*)YCbCr;
    int      image_width  = w;
    int      image_height = h;

    struct jpeg_compress_struct cinfo;
    struct jpeg_error_mgr jerr;

    JSAMPROW row_pointer[1];    /* pointer to JSAMPLE row[s] */
    int row_stride;             /* physical row width in image buffer */

    cinfo.err = jpeg_std_error(&jerr);
    jpeg_create_compress(&cinfo);

    jpeg_stdio_dest(&cinfo, outfile);

    cinfo.image_width = image_width;
    cinfo.image_height = image_height;
    cinfo.input_components = 3;         /* # of color components per pixel */
    cinfo.in_color_space = JCS_YCbCr; /* colorspace of input image */

    jpeg_set_defaults(&cinfo);

    jpeg_set_quality(&cinfo,
                     quality, TRUE /* limit to baseline-JPEG values */);
    
    jpeg_start_compress(&cinfo, TRUE);

    row_stride = image_width * 3;       /* JSAMPLEs per row in image_buffer */

    while (cinfo.next_scanline < cinfo.image_height) {
        row_pointer[0] = & image_buffer[cinfo.next_scanline * row_stride];
        (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
    }

    jpeg_finish_compress(&cinfo);

    jpeg_destroy_compress(&cinfo);
}

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