Legacy ImageMagick Discussions Archive

Hi,

I have an original image, I scale it and remove the transparence

but I randomly found one image, the output image is slightly different from original image anyone knows why this happening?

the command I am using is to trim transparent space is
convert SHIRT_ART_IMAGE1.png -format "%@" +write info: -trim +repage -bordercolor none -border 5 SHIRT_ART_IMAGE1_trim.png

image compare url: https://ibb.co/WHrtTtW

Post the input image alone. It is likely a profile issue.

What version of IM, on what platform?

I suggest you link to actual PNG files, not a screen shot.

yeah, but the image is 16MB, could you recommend a place I can upload image?
the version we use IM is ImageMagick = 6.9.4_1;

original image: https://drive.google.com/open?id=1ufx2A ... XZMolPcnf1
output image: https://drive.google.com/open?id=122q_p ... mGJcV0XuFz

This command works fine for me with no color change using ImageMagick 6.9.10.67 Q16 Mac OSX with libpng @1.6.36.

My guess is that it has to do with the version of libpng you have installed or with the version of ImageMagick.

What are your versions and platform/OS?

I can see no difference between the linked images, except for the border. They have partial transparency, so when viewed against a dark/light chequerboard background, the dark/light squares occur at different places.

@fmw42

when I run ./convert on my remote host I saw this info
Version: ImageMagick 6.9.4-1 Q16 x86_64 2019-09-29 http://www.imagemagick.org

for platform version, I run this command, and here is output uname -a
Linux mftp-ygw-p-f-2-1a-1ebf0e1c.us-east-1.amazon.com 4.9.184-0.1.ac.235.83.329.metal1.x86_64 #1 SMP Tue Jul 30 17:17:50 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

@snibgo

I saw there are some faded color on the original pic and there are not on processed image, could we take it as difference?

Your Imagemagick is ancient, though currently patched. But Linux distributions often only patch for security. So it is possible there is a bug. I saw no difference.

Try

convert -list format

and see what version you have for PNG.

niyanwen wrote: I saw there are some faded color on the original pic and there are not on processed image, could we take it as difference?

Where? If you have a chequerboard background, or any non-constant background, that will create a difference. But the difference is because of the way you are viewing.

Hi,
I run the convert- list format, and below is what I got
PNG* rw- Portable Network Graphics (libpng 1.6.28)
See http://www.libpng.org/ for details about the PNG format.
PNG00* rw- PNG inheriting bit-depth, color-type from original if possible
PNG24* rw- opaque or binary transparent 24-bit RGB (zlib 1.2.11)
PNG32* rw- opaque or transparent 32-bit RGBA
PNG48* rw- opaque or binary transparent 48-bit RGB
PNG64* rw- opaque or transparent 64-bit RGBA
PNG8* rw- 8-bit indexed with optional binary transparency

Hi, @snibog

I am new to image processing, could you recommend what's the right way to view it? like by which software?

I used GMIP to take a look and looks like the original image has transparency in the middle and scaled image hasn't transparency, could we consider this as a difference?

What scaling? Your original post command line has no scaling! What was your exact command? Your PNG version libpng 1.6.28 is a bit old. You might consider upgrading.