Antialiasing filter having no effect

[nekivud]

I have an image and am trying to apply the antialiasing filter.  I have followed the instructions here, and have gotten the filter to work correctly using the same sample image as in the instructions.  However, when I try to use my own image the filter has no effect, i.e. nothing visibly changes.  The image originally had a transparent background, which I thought might be the issue, so I converted the image to be only black pixels on a white background (exactly like the sample image), but the filter still has no effect.

I'm brand new to GIMP, and I'd appreciate any help with this, thanks!

Sample image from GIMP instructions:
   

My image:
   

[Blighty]

It works on your image, but you need to zoom in close to be able to see the results.

Another way is to use Filters > Blur > Gaussian Blur with a small value (about 0,5).

[rich2005]

Your image is an Indexed png and the colormap shows 255 black entries and 1 white entry. You do not get semi-transparency with indexed images, it is either all or nothing, the equivalent is dithering.



For the antialiasing filter to work, change to RGB colorspace Image -> Mode -> RGB

If you desperately need the image in indexed mode, change back to Indexed Image -> Mode -> Indexed and in the export dialogue enable dithering and maybe 12 colours gets something like this:



edit I should add, If you have your original in RGB mode and a transparent background, the easiest way to apply a blur as Blighty's post is use the tileable blur with a value of 2.

[Blighty]

(02-12-2019, 03:20 PM)rich2005 Wrote: Your image is an Indexed png and the colormap shows 255 black entries and 1 white entry.

That is strange. When I open that image it is RGB with 2 colours.

(But the last few days I have also been having problems with images where the transparent areas get changed to black - saving to disk first and then opening in Gimp solves this)

[Ofnuts]

Yes, I downloaded the image from the post and file says it's a regular PNG (8-bit/color RGB, indexed ones are 8-bit colormap). Gimp loads it as an RGB image.

[nekivud]

That worked. Thanks so much, I appreciate the help!

[rich2005]

(02-12-2019, 04:07 PM)Ofnuts Wrote: Yes, I downloaded the image from the post and file says it's a regular PNG (8-bit/color RGB, indexed ones are 8-bit colormap). Gimp loads it as an RGB image.

Yep, my fault. The difference between download and save-as.