Force a PNG export to a format?

psaldorn · September 15, 2025, 10:54am

Hey, this may seem like a basic question but I need all my PNGs to be the same format, RGBA8, but if there are no visible transparent pixels in the image I can’t see how to force Aseprite to offer me the choice?

This is to prevent exceptions in Godot when trying to blit images of different formats.

Some sprites can have a transparent pixel to get around it but some cannot.

Thanks.

behreandtjeremy · September 16, 2025, 12:12am

As far as I can tell, the choice of 32bpp RGBA vs. 24bpp RGB png export cannot be made directly in Aseprite.

To see the png export source code:

github.com/aseprite/aseprite

src/app/file/png_format.cpp

main


      
          if (setjmp(png_jmpbuf(png)))
            return false;
          
          png_init_io(png, fp);
          
          const FileAbstractImage* img = fop->abstractImageToSave();
          const ImageSpec spec = img->spec();
          
          switch (spec.colorMode()) {
            case ColorMode::RGB:
              color_type = (img->needAlpha() || fix_one_alpha_pixel ? PNG_COLOR_TYPE_RGB_ALPHA :
                                                                      PNG_COLOR_TYPE_RGB);
              break;
            case ColorMode::GRAYSCALE:
              color_type = (img->needAlpha() || fix_one_alpha_pixel ? PNG_COLOR_TYPE_GRAY_ALPHA :
                                                                      PNG_COLOR_TYPE_GRAY);
              break;
            case ColorMode::INDEXED:
              if (fix_one_alpha_pixel)
                color_type = PNG_COLOR_TYPE_RGB_ALPHA;
              else

The following are guesses based on a quick glance at the code above:

Do any of the sprites that save to 24bpp have a Background layer in the timeline? (A background layer’s name is underlined in the timeline.) If the sprites do, and you want 32bpp RGBA, then try converting each background layer to a regular layer and re-export.

If that doesn’t work, when you save as a png, try going to File > Export > Export As. Set Export for Twitter to true. This will also set the alpha of one of the pixels – likely the one in the bottom-right corner – to 254.

Similar thread:

psaldorn · September 22, 2025, 1:37pm

Shame, but having random missing pixels isn’t an option for me. A way to set needAlpha() to true appears to be what I want. I’ll have to use external tools to modify the files after export, which will be a pain.

Thanks for the info!