OptiPNG / Bugs / #21 Bad reduccion palette in first execution for b/w image

#21 Bad reduccion palette in first execution for b/w image

Status: open-accepted

Owner: Cosmin Truta

Labels: None

Priority: 5

Updated: 2023-11-03

Created: 2010-05-16

Creator: Silicon

Private: No

I made a compress image with OptiPNG v0.6.4
I used this command line: optipng -o3 -i0 -log=optipng.log img11.png
If first execution, OptiPNG say \"8 bits/pixel, 256 colors in palette. Reducing image to 8 bits/pixel, grayscale\"
In second execution, OptiPNG say \"8 bits/pixel, grayscale. Reducing image to 2 bits/pixel, 4 colors in palette\"

The same happend with -o2 to -o7
I attach the log file, and the image without compress.

Discussion

Silicon - 2010-05-16

log_png.zip

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Cosmin Truta - 2010-09-05

Thanks for the report. I have finally found some time to look at it.

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Cosmin Truta - 2010-09-05

assigned_to: nobody --> cosmin

status: open --> open-accepted
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Andrew - 2023-11-03

Tested with OptiPNG.exe v0.7.7 (27-Dec-2017), Win32.
Confirmed. This 8-bit indexed image is more optimally stored as 2-bit indexed.
This reduction should be evaluated, in addition to grayscale 8 bit. The extra run should not be necessary.

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Bad reduccion palette in first execution for b/w image

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#21 Bad reduccion palette in first execution for b/w image

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