手机网站设计开发,怎样安装微信小程序,sem是什么牌子,关于我校校园网站建设的调研报告jpg压缩原理可以参考这篇文章http://hi.baidu.com/tiandsp/item/f5a2dcde6ef1405bd73aae41#xff0c;我很早以前转的一篇文章。 没有使用libjpeg的压缩代码可以看看这篇文章http://hi.baidu.com/tiandsp/item/9b5843c58a3b4474cfd4f841#xff0c;也是我很早以前转的。 这次… jpg压缩原理可以参考这篇文章http://hi.baidu.com/tiandsp/item/f5a2dcde6ef1405bd73aae41我很早以前转的一篇文章。 没有使用libjpeg的压缩代码可以看看这篇文章http://hi.baidu.com/tiandsp/item/9b5843c58a3b4474cfd4f841也是我很早以前转的。 这次使用libjpeg库压缩和上一篇的解压正好对应起来有好多函数名称我都是对称的起的所以结合起来看效果更好。 和上一篇一样只能处理24位和8位的图像。 代码如下 #include iostream
#include stdio.h
extern C{
#include jpeglib.h
};
#pragma comment(lib,jpeg.lib)
using namespace std;#pragma pack(2) //两字节对齐否则bmp_fileheader会占16Byte
struct bmp_fileheader
{unsigned short bfType; //若不对齐这个会占4Byteunsigned long bfSize;unsigned short bfReverved1;unsigned short bfReverved2;unsigned long bfOffBits;
};struct bmp_infoheader
{unsigned long biSize;unsigned long biWidth;unsigned long biHeight;unsigned short biPlanes;unsigned short biBitCount;unsigned long biCompression;unsigned long biSizeImage;unsigned long biXPelsPerMeter;unsigned long biYpelsPerMeter;unsigned long biClrUsed;unsigned long biClrImportant;
};FILE *input_file;
FILE *output_file;struct bmp_fileheader bfh;
struct bmp_infoheader bih;unsigned char *src_buffer;
unsigned char *dst_buffer;void read_bmp_header()
{ fread(bfh,sizeof(struct bmp_fileheader),1,input_file);fread(bih,sizeof(struct bmp_infoheader),1,input_file);
}void read_bmp_data()
{fseek(input_file,bfh.bfOffBits,SEEK_SET);src_buffernew unsigned char[bih.biWidth*bih.biHeight*bih.biBitCount/8];fread(src_buffer,sizeof(unsigned char)*bih.biWidth*bih.biHeight*bih.biBitCount/8,1,input_file);unsigned long widthbih.biWidth;unsigned long heightbih.biHeight;unsigned short depthunsigned short(bih.biBitCount/8);unsigned char *src_point;unsigned char *dst_point;dst_buffernew unsigned char[width*height*depth]; src_pointsrc_bufferwidth*depth*(height-1);dst_pointdst_bufferwidth*depth*(height-1);for (unsigned long i0;iheight;i){for (unsigned long j0;jwidth*depth;jdepth){if (depth1) //处理灰度图{dst_point[j]src_point[j];}if (depth3) //处理彩色图{dst_point[j2]src_point[j0];dst_point[j1]src_point[j1];dst_point[j0]src_point[j2];}}dst_point-width*depth;src_point-width*depth;}
}void synthese_jpeg()
{struct jpeg_compress_struct cinfo;struct jpeg_error_mgr jerr;JSAMPARRAY buffer;unsigned long widthbih.biWidth;unsigned long heightbih.biHeight;unsigned short depthunsigned short(bih.biBitCount/8);unsigned char *point;cinfo.errjpeg_std_error(jerr); //libjpeg各种配置jpeg_create_compress(cinfo);jpeg_stdio_dest(cinfo,output_file);cinfo.image_widthwidth;cinfo.image_heightheight;cinfo.input_componentsdepth;if (depth1)cinfo.in_color_spaceJCS_GRAYSCALE;elsecinfo.in_color_spaceJCS_RGB;jpeg_set_defaults(cinfo);jpeg_set_quality(cinfo,20,TRUE); //中间的值为压缩质量越大质量越好jpeg_start_compress(cinfo,TRUE);buffer(*cinfo.mem-alloc_sarray)((j_common_ptr)cinfo,JPOOL_IMAGE,width*depth,1);pointdst_bufferwidth*depth*(height-1);while (cinfo.next_scanlineheight){memcpy(*buffer,point,width*depth);jpeg_write_scanlines(cinfo,buffer,1);point-width*depth;}jpeg_finish_compress(cinfo);jpeg_destroy_compress(cinfo);
}int main()
{input_filefopen(lena_gray.bmp,rb);output_filefopen(lena.jpg,wb);read_bmp_header();read_bmp_data();synthese_jpeg();fclose(input_file);fclose(output_file);delete[] src_buffer;delete[] dst_buffer;coutgood job.endl;cin.get();return 0;
} 转载于:https://www.cnblogs.com/tiandsp/archive/2012/12/03/2799561.html
