C语言实现BMP转换JPG

/****************************************************************************
名称：   jpeg.c
功能：   linux下bmp转化为jpeg程序源代码
日期：   2010.01.26
注意：   编译时加“-ljpeg”（gcc -o bmp2jpg jpeg.c -ljpeg）
*****************************************************************************/
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <linux/videodev.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/timeb.h>
#include <jpeglib.h>#define JPEG_QUALITY 95 //图片质量int Bmp2Jpg（const char *bmp_file, const char *jeg_file, const int width, const int height）
{
    FILE *fd;
    int ret;
    unsigned char *data;
    long sizeImage;
    int depth = 3;
    JSAMPROW * row_pointer;
    long rgb_index = 0;
    int i=0;
    struct jpeg_compress_struct cinfo;
    struct jpeg_error_mgr jerr;
    FILE *outfile;
    ;
    // Read bmp image data
    sizeImage = width*height*3;
    data = （unsigned char*）malloc（sizeImage）;
    fd = fopen（bmp_file, "rb"）;
    if（！fd）
    {
        printf（"ERROR1: Can not open the image. "）;
        free（data）;
        return -1;
    }

    fseek（fd, 54, SEEK_SET）;
    ret = fread（data, sizeof（unsigned char）*sizeImage, 1, fd）;
    if（ret == 0）
    {
        if（ferror（fd））
        {
            printf（" ERROR2: Can not read the pixel data. "）;
            free（data）;
            fclose（fd）;
            return -1;
        }
    }    //Convert BMP to JPG
    cinfo.err = jpeg_std_error（&jerr）;
    //* Now we can initialize the JPEG compression object.
    jpeg_create_compress（&cinfo）;    if （（outfile = fopen（jeg_file, "wb"）） == NULL）
    {
        fprintf（stderr, "can"t open %s ", jeg_file）;
        return -1;
    }
    jpeg_stdio_dest（&cinfo, outfile）;    cinfo.image_width = width;             //* image width and height, in pixels
    cinfo.image_height = height;
    cinfo.input_components = depth;    //* # of color components per pixel
    cinfo.in_color_space = JCS_RGB;     //* colorspace of input image
    jpeg_set_defaults（&cinfo）;

     //Now you can set any non-default parameters you wish to.
     //Here we just illustrate the use of quality （quantization table） scaling:    jpeg_set_quality（&cinfo, JPEG_QUALITY, TRUE ）; //* limit to baseline-JPEG values
    jpeg_start_compress（&cinfo, TRUE）;

    //一次写入
    int j=0;
    row_pointer = malloc（height*width*3）;
    char * line[300];    for（i=0;i<height;i++）
    {
        unsigned char * lineData = NULL;
        lineData = malloc（width*3）;
        line[i]=lineData;
        for（j=0;j<width;j++）
        {
            lineData[j*3+2] = data[rgb_index];
            rgb_index ++;
            lineData[j*3+1] = data[rgb_index];
            rgb_index ++;
            lineData[j*3+0] = data[rgb_index];
            rgb_index ++;
        }
        row_pointer[height-i-1] = lineData;
    }
    jpeg_write_scanlines（&cinfo, row_pointer, height）;
    jpeg_finish_compress（&cinfo）;
    jpeg_destroy_compress（&cinfo）;
    for （i=0; i<height; i++）
    {
        free（line[i]）;
    }
    free（row_pointer）;
    free（data）;
    fclose（fd）;
    fclose（outfile）;    return 0;
}