參考很多人的程序，使用JPEGlib 源代碼：
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#include <stdio.h>
#include <unistd.h>
#include <jpeglib.h>
#include "head.h" //IMGWIDTH and IMGHEIGHT
void rgb_to_jpeg (char *filename, unsigned char *img, /
int quality, int gray)
{
struct jpeg_compress_struct jcoms;
struct jpeg_error_mgr jerr; /* More stuff */
FILE *fp; /* target file */
JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */
int line_length, m; /* physical row width in image buffer */
unsigned char *line;
if(debug)
printf("begin to start compress!/n");
jcoms.err = jpeg_std_error(&jerr);
jpeg_create_compress(&jcoms);
if(debug)
printf("create compress OK!/n");
if ((fp = fopen(filename, "w")) == NULL)
{
fprintf(stderr, "can't open %s/n", filename);
exit(1);
}
jpeg_stdio_dest(&jcoms, fp);
jcoms.image_width = IMGWIDTH;
jcoms.image_height = IMGHEIGHT;
jcoms.input_components = gray ? 1 : 3;//3 colour
jcoms.in_color_space = gray ? /
JCS_GRAYSCALE : JCS_RGB；/*colorspace*/
jpeg_set_defaults(&jcoms);
jpeg_set_quality(&jcoms, quality, TRUE);/* limit to baseline-JPEG values */
if(debug)
printf("set quality OK!/n");
jpeg_start_compress(&jcoms, TRUE);
if(debug)
printf("start compress OK!/n");
line_length = gray ? IMGWIDTH : IMGWIDTH * 3;
/* JSAMPLEs per row in image_buffer */
if(debug)
printf("begin to write scanlines/n");
for (m = 0, line = img; m < IMGHEIGHT; /
m++, line +=line_length)
jpeg_write_scanlines(&jcoms, &line, 1);
/* Step 6: Finish compression */
jpeg_finish_compress(&jcoms);
if (debug)
printf("finish compress OK!/n");
/* to read the jpg data to the image buffer*/
/* After finish_compress, we can close the output file. */
fclose(fp);
jpeg_destroy_compress(&jcoms);
if(debug)
printf("destroy compress OK!/n");
//return statbuf.st_size;
/* And we're done! */
}