comp.graphics.algorithms

Subject: Re: Calculate minimum compressed file size for a JPEG image

Chris,

here are some test results:
Photoshop7-standard, Photoshop7-optimized, Hoffmann,
always min.quality to max.quality for pure white RGB,
number of bytes:

16*16 pixels:
PhS-S--- 513-663
PhS-O--- 304-306
Hoff-----630-632

160*160 pixels:
PhS-S--- 768-2291
PhS-O--- 425-603
Hoff---- 1026-1028

Header, Quantization- and Huffman-tables are always
necessary, but it seems, that PhS-O shrinks the tables
as well (e.g. by the knowledge that the image doesn't
contain color).

PhS was applied by 'Save for Web', which doesn't embed
metadata. The optimization algorithm is unknown.

Best regards --Gernot Hoffmann

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