正如@PlinyTheElder 所提到的，DCT 信息可以為您提供運動模糊。我從下面的repo中附上了代碼片段：
代碼在里面C，我不確定是否有 python 綁定libjpeg。否則，您需要創建一個。
/* Fast blur detection using JPEG DCT coefficients
*
* Based on "Blur Determination in the Compressed Domain Using DCT
* Information" by Xavier Marichal, Wei-Ying Ma, and Hong-Jiang Zhang.
*
* Tweak MIN_DCT_VALUE and MAX_HISTOGRAM_VALUE to adjust
* effectiveness. I reduced these values from those given in the
* paper because I find the original to be less effective on large
* JPEGs.
*
* Copyright 2010 Julian Squires <[email protected]>
*/
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <jpeglib.h>
static int min_dct_value = 1; /* -d= */
static float max_histogram_value = 0.005; /* -h= */
static float weights[] = { /* diagonal weighting */
8,7,6,5,4,3,2,1,
1,8,7,6,5,4,3,2,
2,1,8,7,6,5,4,3,
3,2,1,8,7,6,5,4,
4,3,2,1,8,7,6,5,
5,4,3,2,1,8,7,6,
6,5,4,3,2,1,8,7,
7,6,5,4,3,2,1,8
};
static float total_weight = 344;
static inline void update_histogram(JCOEF *block, int *histogram)
{
for(int k = 0; k < DCTSIZE2; k++, block++)
if(abs(*block) > min_dct_value) histogram[k]++;
}
static float compute_blur(int *histogram)
{
float blur = 0.0;
for(int k = 0; k < DCTSIZE2; k++)
if(histogram[k] < max_histogram_value*histogram[0])
blur += weights[k];
blur /= total_weight;
return blur;
}
static int operate_on_image(char *path)
{
struct jpeg_error_mgr jerr;
struct jpeg_decompress_struct cinfo;
jvirt_barray_ptr *coeffp;
JBLOCKARRAY cs;
FILE *in;
int histogram[DCTSIZE2] = {0};
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_decompress(&cinfo);
if((in = fopen(path, "rb")) == NULL) {
fprintf(stderr, "%s: Couldn't open.\n", path);
jpeg_destroy_decompress(&cinfo);
return 0;
}
jpeg_stdio_src(&cinfo, in);
jpeg_read_header(&cinfo, TRUE);
// XXX might be a little faster if we ask for grayscale
coeffp = jpeg_read_coefficients(&cinfo);
/* Note: only looking at the luma; assuming it's the first component. */
for(int i = 0; i < cinfo.comp_info[0].height_in_blocks; i++) {
cs = cinfo.mem->access_virt_barray((j_common_ptr)&cinfo, coeffp[0], i, 1, FALSE);
for(int j = 0; j < cinfo.comp_info[0].width_in_blocks; j++)
update_histogram(cs[0][j], histogram);
}
printf("%f\n", compute_blur(histogram));
// output metadata XXX should be in IPTC etc
// XXX also need to destroy coeffp?
jpeg_destroy_decompress(&cinfo);
return 0;
}
int main(int argc, char **argv)
{
int status, i;
for(status = 0, i = 1; i < argc; i++) {
if(argv[i][0] == '-') {
if(argv[i][1] == 'd')
sscanf(argv[i], "-d=%d", &min_dct_value);
else if(argv[i][1] == 'h')
sscanf(argv[i], "-h=%f", &max_histogram_value);
continue;
}
status |= operate_on_image(argv[i]);
}
return status;
}
編譯代碼：
gcc -std=c99 blur_detection.c -l jpeg -o blur-detection
運行代碼：
./blur-detection <image path>
