C语言实现BMP转换JPG的方法

本文实例讲述了C语言实现BMP转换JPG的方法。分享给大家供大家参考。具体实现方法如下：

/****************************************************************************

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

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#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.\n");

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("\nERROR2: Can not read the pixel data.\n");

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\n", 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

{

unsigned char * lineData = NULL;

lineData = malloc(width*3);

line[i]=lineData;

for(j=0;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

{

free(line[i]);

}

free(row_pointer);

free(data);

fclose(fd);

fclose(outfile);

return 0;

}

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