使用jpeglib进行JPEG压缩字节流

sudo apt-get install libjpeg-dev

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

int main(int argc, char *argv[]) {
    FILE *infile, *outfile;
    struct jpeg_decompress_struct cinfo;
    struct jpeg_compress_struct cinfo_out;
    struct jpeg_error_mgr jerr;
    JSAMPARRAY buffer;
    int row_stride;

    if (argc != 3) {
        fprintf(stderr, "Usage: %s [input file] [output file]\n", argv[0]);
        exit(1);
    }

    infile = fopen(argv[1], "rb");
    if (infile == NULL) {
        fprintf(stderr, "Can't open %s\n", argv[1]);
        exit(1);
    }

    outfile = fopen(argv[2], "wb");
    if (outfile == NULL) {
        fprintf(stderr, "Can't open %s\n", argv[2]);
        exit(1);
    }

    cinfo.err = jpeg_std_error(&jerr);
    jpeg_create_decompress(&cinfo);
    jpeg_stdio_src(&cinfo, infile);
    jpeg_read_header(&cinfo, TRUE);

    jpeg_destroy_decompress(&cinfo);
    jpeg_create_compress(&cinfo_out);
    jpeg_stdio_dest(&cinfo_out, outfile);

    cinfo_out.image_width = cinfo.image_width;
    cinfo_out.image_height = cinfo.image_height;
    cinfo_out.input_components = cinfo.input_components;
    cinfo_out.in_color_space = cinfo.in_color_space;

    jpeg_set_defaults(&cinfo_out);
    jpeg_start_compress(&cinfo_out, TRUE);

    row_stride = cinfo.image_width * cinfo.input_components;
    buffer = (*cinfo_out.mem->alloc_sarray) ((j_common_ptr) &cinfo_out, JPOOL_IMAGE, row_stride, 1);

    while (cinfo.output_scanline < cinfo.output_height) {
        jpeg_read_scanlines(&cinfo, buffer, 1);
        jpeg_write_scanlines(&cinfo_out, buffer, 1);
    }

    jpeg_finish_compress(&cinfo_out);
    jpeg_destroy_compress(&cinfo_out);

    fclose(infile);
    fclose(outfile);

    return 0;
}