Tests relevant to discussion about registering the proposed MAGN chunk for MNG. Images are the well-known Kodak series from ftp.cipr.rpi.edu. The uncompressed raw pixels occupy 27131904 bytes.
All images on this page were made with ImageMagick-5.2.2.
The first column represents the first pass of Adam7 interlacing, and were created with "convert -sample 12.5%" and then expanded for display on this page with "convert -sample 400%". Byte counts are shown for the reduced images.
The second column is a reduced image intended for use with the proposed MAGN chunk, and were created with "convert -quality 23 -geom 128x86" and then expanded for display on this page with "convert -compress none -filter triangle -geom 360x256". Size is reported for the reduced images. I don't know why these operations produce images that are 384 pixels wide.
The third column is the lowest-quality full-scale JPEG that can be made with ImageMagick, made with "convert -quality 1" and then reduced for display on this page with "convert -geom 50%". Size is reported for the full-scale images, and compression ratios are reported when the reduced images are magnified to full scale, not to half scale as on this page. The compression ratio for the center column accounts for the effect of 1886 bytes occupied by 23 JHDR, MAGN, JDAT, and IEND chunks.
I prefer the center column because it's most efficient in file size and also looks slightly clearer than the way the world looks to me when I can't find my glasses.
Adam7 first pass | Q23 Reduced 6 times and magnified |
Q1 |
| Total 318498 bytes (average 85:1 compression) |
Total 29679+1886 bytes (average 860:1 compression) |
Total 97840 bytes (average 277:1 compression) |
| 
| 
|
| 14335 bytes | 1401 bytes | 5062 bytes |
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| 
|
| 12480 bytes | 849 bytes | 3275 bytes |
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| 
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| 12420 bytes | 1200 bytes | 3412 bytes |
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| 
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| 13657 bytes | 1210 bytes | 3502 bytes |
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| 
|
| 16161 bytes | 1819 bytes | 6104 bytes |
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| 
|
| 13984 bytes | 1113 bytes | 4134 bytes |
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| 
|
| 13632 bytes | 1381 bytes | 4060 bytes |
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| 
|
| 16152 bytes | 1909 bytes | 7917 bytes |
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| 
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| 12693 bytes | 1160 bytes | 3830 bytes |
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| 
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| 13338 bytes | 1169 bytes | 3718 bytes |
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| 
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| 13546 bytes | 1215 bytes | 4022 bytes |
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| 
|
| 12467 bytes | 1058 bytes | 3561 bytes |
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| 
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| 16269 bytes | 1517 bytes | 5533 bytes |
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| 
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| 15295 bytes | 1520 bytes | 4390 bytes |
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| 
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| 12755 bytes | 1381 bytes | 4044 bytes |
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| 
|
| 12796 bytes | 992 bytes | 3186 bytes |
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| 
|
| 14265 bytes | 1345 bytes | 3876 bytes |
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| 
|
| 15301 bytes | 1360 bytes | 4154 bytes |
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| 
|
| 14472 bytes | 1188 bytes | 4697 bytes |
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| 
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| 10781 bytes | 1267 bytes | 3875 bytes |
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| 
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| 14283 bytes | 1267 bytes | 4219 bytes |
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| 
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| 14266 bytes | 1174 bytes 3623 bytes | |
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| 
|
| 13050 bytes | 1289 bytes | 3646 bytes |
| Total 318498 bytes (average 85:1 compression) |
Total 29679+1886 bytes (average 860:1 compression) |
Total 97840 bytes (average 277:1 compression) |
| bytes shown are the sizes before magnifying | ||