Sometime when I import an image into the rom, it doubles the size of the background. Is there a way to fix this? I have tried changing the image in Photoshop, but the quality gets bad when you decrease size. What is causing some images to double in size and others to stay the same? I have no other way of ripping the image I want ingame. Any ideas?

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I can't quite figure out what makes the images larger. I am ripping the background images out of other games. I am starting to think that maybe it is because the other games use different screen sizes. I don't know. So I rip the original image and then import into my rom. In NSMB it appears maybe 33% larger. But what I don't get is the image is a pre-determined size. So is it NSMB rendering the image larger? Or the game I am ripping from rendering the image smaller?

So back to screen size. Different games and consoles use different screen sizes. Maybe ripping backgrounds and/or importing them causes size or rendering issues between consoles. Tiles always end up the same at 16X16. But backgrounds seem to not render the same.

I just can't figure out where the resizing occurs.

NSMB background images are ALWAYS 512x512 pixels.
If you import a .png file that is NOT 512x512, very bad things may happen.

So, if you want to import a smaller BG, you should edit it in GIMP or Photoshop, and make it 512x512. If you don't want to resize the BG, just make it "loop".

For example, if you have a 256x256 BG, then make a 512x512 BG, copying the 256px one 4 times.

I always make them 512x512. And I also loop them. I am referring to actual image size based on pixels not canvas ending up different ingame.