What are the limitations on opening large image-files?

[tomatoSauce23]

Hi, I have a large 1.89GB PNG that is [51k x 42k] pixels big, it's a large map. It takes GIMP about 90 seconds to open it and to get it ready for me to view and edit. I have 16GB of RAM and Windows Task Manager says GIMP uses 8.5GB of it to display this PNG. My Dell laptop was brand-new a year ago, so the CPU's pretty-good for a laptop; the GPU is a baked-in standard Intel one, that manages most things without a problem except for demanding games.

It's not a problem for me that it should be slow to load and edit this image, as I would otherwise cut the PNG up into smaller sections; but I'm curious as to what exactly the limitations are. If I had to guess I would say it is either the CPU or GPU that can't load the large file into GIMP more quickly than that, no matter how much RAM it had supporting it. the Irfanview app could not open the image, so GIMP is doing a better job than it at least. I don't know how other image-editing software would compare—Adobe etc. .

[Ofnuts]

(11-09-2024, 12:02 PM)tomatoSauce23 Wrote: Hi, I have a large 1.89GB PNG that is [51k x 42k] pixels big, it's a large map. It takes GIMP about 90 seconds to open it and to get it ready for me to view and edit. I have 16GB of RAM and Windows Task Manager says GIMP uses 8.5GB of it to display this PNG. My Dell laptop was brand-new a year ago, so the CPU's pretty-good for a laptop; the GPU is a baked-in standard Intel one, that manages most things without a problem except for demanding games.

It's not a problem for me that it should be slow to load and edit this image, as I would otherwise cut the PNG up into smaller sections; but I'm curious as to what exactly the limitations are. If I had to guess I would say it is either the CPU or GPU that can't load the large file into GIMP more quickly than that, no matter how much RAM it had supporting it. the Irfanview app could not open the image, so GIMP is doing a better job than it at least. I don't know how other image-editing software would compare—Adobe etc. .

Not too surprised. Your image is 2Gpix, so assuming 4 bytes per pixel (RGBA channels), a single layer of the image is around 8GB. And Gimp is probably needing at least three times this: the layer, the composite image to display, and a buffer... So more around 24GB. Since you have only a cute 16GB, at least 8GB (and probably more like 12GB) have to be swapped to disk by your system (or directly by Gimp, see the Tile cache size in the Preferences). And since the image is scaled to fit the screen on load, there is  a giant scale operation taking place on two gigapixels before you can even see it.

And Gimp is probably not using your GPU by default, but I don't think this makes much of a difference.

[PixLab]

(11-09-2024, 12:02 PM)tomatoSauce23 Wrote: Hi, I have a large 1.89GB PNG that is [51k x 42k] pixels.....//

To add to Ofnuts, but in very direct way ➤ triple your RAM! Get 48 or 64 GB
I have 24Gb RAM, for an image half the size of yours, if I had 1 layer and use 1 or 2 filters, my computer hang for a while, and if I move a layer or try transform it, I have time to make a coffee, drink it, and cook something.