I've converted this through other programs (ImageMagick, Preview) and it doesn't produce these lines. Since ImageMagick should be using the same PNG delegate as GraphicsMagick (libpng v. 1.2.49) I'm less inclined to believe it's the delegate (but not certain).
Running gm -identify -verbose on the images, I noticed two major differences: the Png:IHDR.bit-depth-orig: value on the original is 16 and the latter value is 8, and secondly the size of the image drops significantly. ImageMagick preserves these, but I don't know what's going on "under the hood" with ImageMagick, if it's just copying data directly or the like.
I've tried using -set with the value as well as -depth 16, but neither seems to work (I could be executing wrong).
I'm using GraphicsMagick 1.3.18 on CentOS 6.2. Here's a dump of the features we've got on:
Feature Support:
Thread Safe yes
Large Files (> 32 bit) yes
Large Memory (> 32 bit) yes
BZIP yes
DPS no
FlashPix no
FreeType yes
Ghostscript (Library) no
JBIG no
JPEG-2000 no
JPEG yes
Little CMS yes
Loadable Modules yes
OpenMP no
PNG yes
TIFF yes
TRIO no
UMEM no
WMF yes
X11 yes
XML yes
ZLIB yes
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A simple conversion with a PNG is producing vertical lines in the outputted image.
command line one-liner is:
gm convert original_without_lines.png new.png
Original image is:
http://imgur.com/HeVXxdq
New image is:
http://imgur.com/aeZfL5J
I've converted this through other programs (ImageMagick, Preview) and it doesn't produce these lines. Since ImageMagick should be using the same PNG delegate as GraphicsMagick (libpng v. 1.2.49) I'm less inclined to believe it's the delegate (but not certain).
Running gm -identify -verbose on the images, I noticed two major differences: the Png:IHDR.bit-depth-orig: value on the original is 16 and the latter value is 8, and secondly the size of the image drops significantly. ImageMagick preserves these, but I don't know what's going on "under the hood" with ImageMagick, if it's just copying data directly or the like.
I've tried using -set with the value as well as -depth 16, but neither seems to work (I could be executing wrong).
I'm using GraphicsMagick 1.3.18 on CentOS 6.2. Here's a dump of the features we've got on:
Feature Support:
Thread Safe yes
Large Files (> 32 bit) yes
Large Memory (> 32 bit) yes
BZIP yes
DPS no
FlashPix no
FreeType yes
Ghostscript (Library) no
JBIG no
JPEG-2000 no
JPEG yes
Little CMS yes
Loadable Modules yes
OpenMP no
PNG yes
TIFF yes
TRIO no
UMEM no
WMF yes
X11 yes
XML yes
ZLIB yes