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Ticket UUID: 3405839
Title: Writing PNG images sometimes generates wrong sBIT chunk
Type: Bug Version: obsolete: 8.6b2
Submitter: sbron Created on: 2011-09-07 20:25:47
Subsystem: 41. Photo Images Assigned To: dkf
Priority: 7 High Severity:
Status: Closed Last Modified: 2011-09-27 17:39:57
Resolution: Fixed Closed By: dkf
    Closed on: 2011-09-27 10:39:57
Description:
When writing PNG images, the sBIT chunk is always written with a length of 4. This should actually vary depending on the color type.

Script to reproduce the problem:
image create photo foo -width 20 -height 20
foo write foo.png -format png

This writes a PNG file with color type 4, which should have an sBIT chunk of 2 bytes.
User Comments: dkf added on 2011-09-27 17:39:57:

allow_comments - 1

Write the sDAT chunk correctly (even handling cases which we probably don't generate) by trimming its length, since we always use the same bit depth.