huge differences between lossless images

Summary:

Lossless files produced by Phatch from the same image + a watermark look very very different.

huge differences between lossless images

DrSlony 30 Apr 2009 15:15

I took a large JPG photo and a PNG watermark with alpha and used phatch to generate smaller watermarked images. I saved using TIFF and PNG (because I want to use no subsampling in my JPG files and phatch doesn't currently allow me to do that, so I batch convert them to JPG with no subsampling in another program). Look at the files in the linked archive, I named them according to what program I made them in.
All the images in the archive were made from a lossless TIFF image made by phatch, except for "00 gimp.tif" which I made completely using Gimp, to compare.
"01 phatch.png" is a PNG straight from patch
"02 phatch.tif" is a TIFF straight from phatch.
"03 phatch gimp.png" i took the TIFF from Phatch and saved it as PNG in Gimp
"04 phatch digikam.jpg" i took the TIFF from Phatch and saved it as JPG in digiKam
"05 phatch gimp.jpg" i took the TIFF from Phatch and saved it as JPG in Gimp
The JPG files use no subsampling.
I also included the watermark I used and the .phatch file.

Download [3.4MB] http://www.panopixel.org/downloads/phatch_lossless_image_quirks.tar.bz2

Re: huge differences between lossless images

DrSlony 01 May 2009 17:52

The JPG files are YCbCr and the tiff/png are RGB, so this explains the jpg/lossless difference, but then the PNG and TIFF should be identical since they're both RGB, shouldn't they?

Re: huge differences between lossless images

stani 08 May 2009 15:23

In which way the png and the tif are different?

Re: huge differences between lossless images

DrSlony 23 Jun 2009 15:34

The watermark.

Re: huge differences between lossless images

stani 23 Jun 2009 19:08

Well this is not about Phatch, but about the Python Image library behind it. I can't really help you with this.