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Now also show jpeg quality in view.cgi program under view details
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,161 @@ | ||
| //-------------------------------------------------------------------------- | ||
| // Program to pull the information out of various types of EXIF digital | ||
| // camera files and show it in a reasonably consistent way | ||
| // | ||
| // This module handles guessing of jpeg quality from quantization table | ||
| // | ||
| // Using code from Andy Spiegl | ||
| //-------------------------------------------------------------------------- | ||
| #include "jhead.h" | ||
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| // for the DQT marker -- start -- | ||
| // Sample quantization tables from JPEG spec --- only needed for | ||
| // guesstimate of quality factor. Note these are in zigzag order. | ||
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| static int std_luminance_quant_tbl[64] = { | ||
| 16, 11, 12, 14, 12, 10, 16, 14, | ||
| 13, 14, 18, 17, 16, 19, 24, 40, | ||
| 26, 24, 22, 22, 24, 49, 35, 37, | ||
| 29, 40, 58, 51, 61, 60, 57, 51, | ||
| 56, 55, 64, 72, 92, 78, 64, 68, | ||
| 87, 69, 55, 56, 80, 109, 81, 87, | ||
| 95, 98, 103, 104, 103, 62, 77, 113, | ||
| 121, 112, 100, 120, 92, 101, 103, 99 | ||
| }; | ||
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| static int std_chrominance_quant_tbl[64] = { | ||
| 17, 18, 18, 24, 21, 24, 47, 26, | ||
| 26, 47, 99, 66, 56, 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, 99, 99, 99, 99, | ||
| 99, 99, 99, 99, 99, 99, 99, 99 | ||
| }; | ||
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| static int *deftabs[2] = | ||
| { std_luminance_quant_tbl, std_chrominance_quant_tbl }; | ||
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| // jpeg_zigzag_order[i] is the zigzag-order position of the i'th element | ||
| // of a DCT block read in natural order (left to right, top to bottom). | ||
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| static int jpeg_zigzag_order[64] = { | ||
| 0, 1, 5, 6, 14, 15, 27, 28, | ||
| 2, 4, 7, 13, 16, 26, 29, 42, | ||
| 3, 8, 12, 17, 25, 30, 41, 43, | ||
| 9, 11, 18, 24, 31, 40, 44, 53, | ||
| 10, 19, 23, 32, 39, 45, 52, 54, | ||
| 20, 22, 33, 38, 46, 51, 55, 60, | ||
| 21, 34, 37, 47, 50, 56, 59, 61, | ||
| 35, 36, 48, 49, 57, 58, 62, 63 | ||
| }; | ||
| // for the DQT marker -- end -- | ||
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| //-------------------------------------------------------------------------- | ||
| // Process an DQT (Define Quantization Table) marker. | ||
| // | ||
| // Code mostly "stolen" from jpegdump: | ||
| // Copyright (c) 1992 Handmade Software, Inc. | ||
| // by Allan N. Hessenflow | ||
| // | ||
| // We want to print out the "Approximate quality factor" | ||
| //-------------------------------------------------------------------------- | ||
| // | ||
| // The numbers printed in the `Approximate quality factor' line are as follows: | ||
| // Quality: an estimate of the quality factor used when cjpeg was run. | ||
| // Scaling factor (scale): mean ratio between quantization table entries | ||
| // and JPEG sample table entries, times 100. | ||
| // Variance (var): squared standard deviation of the above ratio. | ||
| // If this is larger than about 2, then the table is not a simple | ||
| // multiple of the standard's sample table, so the file was NOT | ||
| // generated by cjpeg and the quality estimate is dubious. | ||
| //-------------------------------------------------------------------------- | ||
| void process_DQT (const uchar * Data, int length) | ||
| { | ||
| int a; | ||
| int c; | ||
| int tableindex, coefindex, row, col; | ||
| unsigned int table[64]; | ||
| int *reftable = NULL; | ||
| double cumsf = 0.0, cumsf2 = 0.0; | ||
| int allones = 1; | ||
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| a=2; // first two bytes is length | ||
| while (a<length) | ||
| { | ||
| c = Data[a++]; | ||
| tableindex = c & 0x0f; | ||
| if (ShowTags>1){ | ||
| printf("DQT: table %d precision %d\n", tableindex, (c>>4) ? 16 : 8); | ||
| } | ||
| if (tableindex < 2){ | ||
| reftable = deftabs[tableindex]; | ||
| } | ||
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| // Read in the table, compute statistics relative to reference table | ||
| if (a+64 > length) { | ||
| ErrNonfatal("DQT section too short",0,0); | ||
| return; | ||
| } | ||
| for (coefindex = 0; coefindex < 64; coefindex++) { | ||
| unsigned int val; | ||
| if (c>>4) { | ||
| register unsigned int temp; | ||
| temp=(unsigned int) (Data[a++]); | ||
| temp *= 256; | ||
| val=(unsigned int) Data[a++] + temp; | ||
| } else { | ||
| val=(unsigned int) Data[a++]; | ||
| } | ||
| table[coefindex] = val; | ||
| if (reftable) { | ||
| double x; | ||
| // scaling factor in percent | ||
| x = 100.0 * (double)val / (double)reftable[coefindex]; | ||
| cumsf += x; | ||
| cumsf2 += x * x; | ||
| // separate check for all-ones table (Q 100) | ||
| if (val != 1) allones = 0; | ||
| } | ||
| } | ||
| // If requested, print table in normal array order | ||
| if (ShowTags>2){ | ||
| for (row=0; row<8; row++) { | ||
| printf(" "); | ||
| for (col=0; col<8; col++) { | ||
| printf("%5u ", table[jpeg_zigzag_order[row*8+col]]); | ||
| } | ||
| printf("\n"); | ||
| } | ||
| } | ||
| // Print summary stats | ||
| if (reftable) { // terse output includes quality | ||
| double qual, var; | ||
| cumsf /= 64.0; // mean scale factor | ||
| cumsf2 /= 64.0; | ||
| var = cumsf2 - (cumsf * cumsf); // variance | ||
| if (allones){ // special case for all-ones table | ||
| qual = 100.0; | ||
| }else if (cumsf <= 100.0){ | ||
| qual = (200.0 - cumsf) / 2.0; | ||
| }else{ | ||
| qual = 5000.0 / cumsf; | ||
| } | ||
| if (ShowTags>1) printf(" "); | ||
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| if (ShowTags){ | ||
| printf("Approximate quality factor for qtable %d: %.0f (scale %.2f, var %.2f)\n", | ||
| tableindex, qual, cumsf, var); | ||
| } | ||
| if (tableindex == 0){ | ||
| ImageInfo.QualityGuess = (int)(qual+0.5); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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