In C when you want to manipulate the screen, you don't manipulate the screen buffer directly, you manipulate a bank of memory. But in Blitz, manipulating a bank of memory seems to be relatively slow, because Poke and Peek seem to be function calls, and not converted directly to memory accesses. And that is why Poke and Peek aren't really any faster than WritepixelFast either. WritePixelFast after all is really writing to a buffer in memory, which is then sent to the video card later for rendering, as far as I know. So they both just access a buffer in memory. But it's the way that they do it that is slower than doing the same thing with an array.
You might be able to redimension an array in Blitz to take advantage of the array speed... I think you can do it in functions, but maybe those have to be a fixed size per function... Hm... But even if you can you still have to copy all your images to arrays to manipulate them like this unless you were able to store all your images in arrays.
So without arrays being able to be redimensioned, and without making ALL your images in array format, then you're stuck. And don't forget either that writepixelfast converts on the fly to the current bitdepth. You'd have to do that yourself too.
You might be able to redimension an array in Blitz to take advantage of the array speed... I think you can do it in functions, but maybe those have to be a fixed size per function... Hm... But even if you can you still have to copy all your images to arrays to manipulate them like this unless you were able to store all your images in arrays.
So without arrays being able to be redimensioned, and without making ALL your images in array format, then you're stuck. And don't forget either that writepixelfast converts on the fly to the current bitdepth. You'd have to do that yourself too.