[经验]

【NanoPi NEO2试用体验】libjpeg库的使用之jpeg压缩

汤权

2017-7-7 09:24:00

2594

上一篇文章是使用libjpeg库进行jpeg图片的解码，现在进行jpeg图片的编码（压缩）。步骤都是一样的，创建编码器，设置源像素数据的格式，设置输出文件句柄，设置输出图片的质量0到100，然后进行编码即可。测试源代码如下：

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include time.h>
#include
#include
#include
#include
#include "jpeglib.h"
#include
#define CLEAR(x) memset (&(x), 0, sizeof (x))
int main (int argc, char **argv)
{
char * filename = "test.jpeg";
unsigned char* yuvData;
int quality = 80;
int image_width = 640;
int image_height = 480;
int i;
yuvData = malloc(640 * 480 * 3);
for(i=0;i<640 * 480;i++)
{
yuvData[i++] = 0xff;
yuvData[i++] = 0x00;
yuvData[i] = 0x00;
}
for(i;i<640 * 480*2;i++)
{
yuvData[i++] = 0x00;
yuvData[i++] = 0xff;
yuvData[i] = 0x00;
}
for(i;i<640 * 480*3;i++)
{
yuvData[i++] = 0x00;
yuvData[i++] = 0x00;
yuvData[i] = 0xff;
}
yuvData[0] = yuvData[1] = yuvData[2] = 0;
printf("LINE:%d,%drn",__LINE__,yuvData);
struct jpeg_compress_struct cinfo;
struct jpeg_error_mgr jerr;
FILE * outfile; // target file
JSAMPROW row_pointer[1]; // pointer to JSAMPLE row[s]
int row_stride; // physical row width in image buffer
JSAMPIMAGE buffer;
unsigned char *pSrc,*pDst;
int band,buf_width[3],buf_height[3];
cinfo.err = jpeg_std_error(&jerr);
printf("LINE:%drn",__LINE__);
jpeg_create_compress(&cinfo);
printf("LINE:%drn",__LINE__);
if ((outfile = fopen(filename, "wb")) == NULL) {
fprintf(stderr, "can't open %sn", filename);
exit(1);
}
jpeg_stdio_dest(&cinfo, outfile);
printf("LINE:%drn",__LINE__);
cinfo.image_width = image_width; // image width and height, in pixels
cinfo.image_height = image_height;
cinfo.input_components = 3; // # of color components per pixel
cinfo.in_color_space = JCS_RGB; //colorspace of input image
jpeg_set_defaults(&cinfo);
jpeg_set_quality(&cinfo, quality, TRUE );
////////////////////////////
// cinfo.raw_data_in = TRUE;不能加这个设置，为什么
cinfo.jpeg_color_space = JCS_YCbCr;
cinfo.comp_info[0].h_samp_factor = 2;
cinfo.comp_info[0].v_samp_factor = 2;
///////////////////////
jpeg_start_compress(&cinfo, TRUE);
printf("LINE:%drn",__LINE__);
while (cinfo.next_scanline < cinfo.image_height)
{
row_pointer[0] = &yuvData[cinfo.next_scanline * cinfo.image_width * cinfo.input_components];
// printf("LINE:%d,%drn",__LINE__,cinfo.next_scanline);
jpeg_write_scanlines(&cinfo, row_pointer, 1);
}
jpeg_finish_compress(&cinfo);
fclose(outfile);
jpeg_destroy_compress(&cinfo);
return 0;
}