I want to allocate memory for 700 MB to 800 MB Image size

Question

I am trying to allocate memory NSImage*originalLocationImage;

NSURL *fileURL = [NSURL fileURLWithPath:originalLocation]; //originalLocation is file path in my disk

originalLocationImage = [[NSImage alloc]initByReferencingURL:fileURL];

NSBitmapImageRep *sourceRep = [[NSBitmapImageRep alloc]initWithData:[SourceImage TIFFRepresentation]]  //this line fails to allocate memory

and it fails for large Images/

and throws error

malloc: *** mmap(size=268435456) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug

for small images it works properly.

any help??

Answer 1

I'd question why you want to load all of the image into memory in the first place - surely dealing with it like a tile set would be a better option?

You are getting this message because, whilst you might have this much memory free, you don't have this much contiguous memory free

Answer 2

If all you want is a preview, you could read it line by line, skipping every n lines and for each line, skip every n pixels. You're left with a (way) smaller image that you can pass through more sophisticated scaling algorithms if necessary, or you can just save it as your thumbnail image or whatever.

Answer 3

Using libjpeg might be an option, it seems to be able to do an optimized sub-scaling up to 16: http://jpegclub.org/djpeg/.

libjpeg is plain C, so you can call it from Objective-C.

Answer 4

If you only want to create a preview of the image, CGImageSource has APIs specifcally for that. They are very first and don't require reading the entire image into memory.