jpeg图像质量参数及icc信息提取

2023-04-05 03:47| 来源: 网络整理| 查看: 265

图像编码算法都有相应的质量参数，如hevc编码中的qp值（值越大，压缩率越高），jpeg中的quality（对应到DCT变换后的量化程度）。最近看了看如何根据jpeg图像中的量化文件统计其quality参数，记录下过程。

jpeg文件中可以携带icc颜色配置信息，这个参数告诉显示器用什么色域来显示图像，如下图文件中包含了Adobe RGB色彩描述文件，icc文件大小通常为几百个字节，嵌入在APP2 marker（0xe2）中。

我的环境：linux centos、libjpeg turbo库

Talk is cheap, Show me your code...

#include #include #include "jpeglib.h" #include #include "turbojpeg.h" #include "cdjpeg.h" //标准亮度分量量化表 static const unsigned int std_luminance_quant_tbl[DCTSIZE2] = { 16, 11, 10, 16, 24, 40, 51, 61, 12, 12, 14, 19, 26, 58, 60, 55, 14, 13, 16, 24, 40, 57, 69, 56, 14, 17, 22, 29, 51, 87, 80, 62, 18, 22, 37, 56, 68, 109, 103, 77, 24, 35, 55, 64, 81, 104, 113, 92, 49, 64, 78, 87, 103, 121, 120, 101, 72, 92, 95, 98, 112, 100, 103, 99 }; //标准色度分量量化表 static const unsigned int std_chrominance_quant_tbl[DCTSIZE2] = { 17, 18, 24, 47, 99, 99, 99, 99, 18, 21, 26, 66, 99, 99, 99, 99, 24, 26, 56, 99, 99, 99, 99, 99, 47, 66, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99 }; const char *subsampName[TJ_NUMSAMP] = { "4:4:4", "4:2:2", "4:2:0", "Grayscale", "4:4:0", "4:1:1" }; const char *colorspaceName[TJ_NUMCS] = { "RGB", "YCbCr", "GRAY", "CMYK", "YCCK" }; //读取JPG文件的质量参数 int ReadJpegInfo(const char *filename, char *icc_filename) { FILE * infile = fopen(filename, "rb"); fseek(infile,0,SEEK_END); //把文件指针移到文件末尾 size_t sz = ftell(infile); //获取文件指针相对文件首的偏移数 fseek(infile,0,SEEK_SET); //把文件指针移到文件头 unsigned char* buffer = new unsigned char[sz]; fread(buffer,1,sz,infile); fclose(infile); //如果不是JPG格式的文件返回-1 if(buffer==NULL || sz quantval[i]; printf("DCTQUA1[%d] = %ld, DCTQUA2[%d] = %ld\n", i, temp1, i, temp2); if(temp1 0) { linear_quality = ceil((float)(temp1 * 100L - 50L)/std_luminance_quant_tbl[i]); //100L表示long int if(linear_quality == 1) tmp_quality = 1; else if(linear_quality == 100) tmp_quality = 50; else if(linear_quality > 100) tmp_quality = ceil((float)5000 / linear_quality); else tmp_quality = 100 - ceil((float)linear_quality/2); aver_quality += tmp_quality; times++; if(aver_times == times) { aver_quality = aver_quality / aver_times; break; } } } if (icc_filename != NULL) { FILE *icc_file; JOCTET *icc_profile; unsigned int icc_len; if ((icc_file = fopen(icc_filename, "wb")) == NULL) { printf("can't open %s\n", icc_filename); } if (jpeg_read_icc_profile(&cinfo, &icc_profile, &icc_len)) { printf("icc_len = %d\n", icc_len); if (fwrite(icc_profile, icc_len, 1, icc_file) msg_code != JWRN_BOGUS_ICC) // printf("no ICC profile data in JPEG file\n"); } jpeg_destroy_decompress(&cinfo); return aver_quality; } // g++ -L /opt/libjpeg-turbo/lib64 -lturbojpeg -ljpeg get_jpg_quality.cpp -o quality // ./quality xxx.jpg int main(int argc, char **argv) { if(argc != 2) { printf("parameter number should set to 2\n"); return -1; } char icc_filename[100] = {0}; sprintf(icc_filename, "%s.icc", argv[1]); printf("quality: %d\n", ReadJpegInfo(argv[1], icc_filename)); return 0; }

运行结果如下，计算得到quality为92.

参考

[1] libjpeg-turbo/libjpeg-turbo

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