Re:Fun Photoshop File Format Facts
by vladdanilov on Thursday March 03, 2016 @02:18PM
(#11219229)
The fun is multiplied by how Photoshop actually renders graphics. For example, 1-pixel drop shadow looks identical to 2-pixel one. When scripting, bounds of vector shapes may be off by 1 or 2 pixels due to some floating point math followed by rounding. Just today stumbled across dithering issues caused by mismatching user-defined and internal color values (https://twitter.com/vmdanilov/status/705262877805039616).
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And there's the fact that its rendering of 1px vector rectangle borders depends on their location. Yup, sometimes they render a little bit thicker[1], which can be fixed by moving it up or down a couple pixels. I kind of hate Photoshop, except it's actually 10x better than anything else at what it does[2]. RIP Fireworks though.
(As of CS 5.5)
1. Photoshop does antialiasing/subpixel rendering on vector shapes, so while "a little bit thicker" is of course 2px, the second row of pixels is blended with what's nearby.
2. Haven't tried GIMP for a couple years though. Also I've switched to Krita for digital painting lately, and actually like it more than PS.