I am using the program Game Maker to create a game using images created with Inkscape. For some reason alpha edges on some images created using 0.91 becomes "dirty", jagged and dark colored, when scaling them, while this has never happened with images created with 0.48 (as far as I know).

Below I linked to two images in my Dropbox, they are unaltered and in their original export size from Inkscape. These are created from the exact same object. I created it in 0.91 and exported to a png that then displays dirty edge but only when scaling the image. Then I exported to png from a 0.48 window instead and this image does NOT show dirty edges when scaling the image! What is the difference between these two images?

0.91(dirty edges on scaling): https://www.dropbox.com/s/v570q8seetnvw ... s.png?dl=0
0.48(no dirty edges on scaling): https://www.dropbox.com/s/9wfhkdcfz8sb1 ... s.png?dl=0

Also below is two screenshots of my game when scaling the images up, using the 0.91 picture on the first image, and 0.48 picture on the second. As you can see on the 0.91 there is black/dirty edges while 0.48 image has fine/normal edges.

What is causing this? Is it a bug that was introduced with 0.91 that somehow sometimes does not create a proper alpha channel? And how do I fix this other than export from 0.48?

0.91 in-game screenshot (dirty edges on scaling):


0.48 in-game screenshot (no dirty edges on scaling):

I'm not sure what you mean by "alpha edges". But I see absolutely no difference between those images in dropbox (viewed through Firefox).

There was a change in how raster images are displayed in Inkscape, with 0.91. But it doesn't sound like you're displaying raster images in Inkscape. It sounds like you're exporting PNGs using Export PNG Image dialog.

Have you changed the anti-aliasing option? Document Properties > Page tab > Display > Use Anti-Aliasing?

toxigames wrote:Below I linked to two images in my Dropbox, they are unaltered and in their original export size from Inkscape. These are created from the exact same object. I created it in 0.91 and exported to a png that then displays dirty edge but only when scaling the image. Then I exported to png from a 0.48 window instead and this image does NOT show dirty edges when scaling the image! What is the difference between these two images?

One difference between the two bitmap exports is the color of the fully transparent pixels (empty background): they are fully transparent white in the PNG exported with Inkscape 0.48; fully transparent black in the PNG exported with Inkscape 0.91.

Attempts to reproduce the "dirty edges" in GIMP 2.9 (adding cloudy background, up- or downscale the image (before or after flattening); with different interpolation methods (None, Linear, Cubic, NoHalo, LoHalo)) failed - the results were as expected, without unwanted artifacts.

~suv wrote:One difference between the two bitmap exports is the color of the fully transparent pixels (empty background): they are fully transparent white in the PNG exported with Inkscape 0.48; fully transparent black in the PNG exported with Inkscape 0.91.

… or the same information stated differently (taken from ImageMagick's identify output):

• 048_no_dirty_edges.png
  Alpha: srgba(255,255,255,0) #FFFFFF00
  Background color: white
• 091_dirty_edges.png
  Alpha: none #00000000
  Background color: white

~suv wrote:One difference between the two bitmap exports is the color of the fully transparent pixels (empty background): they are fully transparent white in the PNG exported with Inkscape 0.48; fully transparent black in the PNG exported with Inkscape 0.91.

Attempts to reproduce the "dirty edges" in GIMP 2.9 (adding cloudy background, up- or downscale the image (before or after flattening); with different interpolation methods (None, Linear, Cubic, NoHalo, LoHalo)) failed - the results were as expected, without unwanted artifacts.

From your post I understand that for whatever the real reason my game development program Game Maker shows black jagged edges on semi transparent (anti-aliased) edges when the PNG is exported with fully transparent black. That must be it then. Is there some way to make Inkscape 0.91 export the PNG's with fully transparent white instead of black?

~suv wrote:

~suv wrote:One difference between the two bitmap exports is the color of the fully transparent pixels (empty background): they are fully transparent white in the PNG exported with Inkscape 0.48; fully transparent black in the PNG exported with Inkscape 0.91.

… or the same information stated differently (taken from ImageMagick's identify output):

• 048_no_dirty_edges.png
  Alpha: srgba(255,255,255,0) #FFFFFF00
  Background color: white
• 091_dirty_edges.png
  Alpha: none #00000000
  Background color: white

~suv, If you have the time to it can I ask you to copy paste the command line you give ImageMagick to print the info you found? I'd like to analyze my images because this happens sometimes, sometimes not, and I can't really figure why or how it happens.

toxigames wrote:(…) can I ask you to copy paste the command line you give ImageMagick to print the info you found?

Verbose information about image:
More information about the 'identify' command:
Online reference: ImageMagick: Command-line Tools: Identify

Thank you! I managed to print the info for a new image, made using 0.91. The image displays bad white edges when scaled down (but nothing when scaling up), but this time it also shows when scaling in any image viewer. This is the info:

Background color: white
Alpha: srgba(255,255,255,0) #FFFFFF00


This is the image:

https://www.dropbox.com/s/owblqsji8nd4n ... 5.zip?dl=0

Do you know why this particular image displays white edges when scaled?

I found out that changing the color of the transparent to brown worked very well in my game. The semi transparent dark green edge on my sprite drawn over light blue and over light brown does not show artifacts when color of transparency is brown. It's a bit annoying though that I have to run ImageMagick on each created png image just to change to brown. Isn't it possible to tell Inkscape to save the png with a browncolored transparency?