ios Decode part of an image

Question

I have a big image which is too big to be loaded into memory but i am only interested in a sub set of pixels within that big image. Is it possible to decode into memory only this subset of pixels? I know that in Android there is a class in the API to do exactly this called BitmapRegionDecoder are something like that

I found CGDataProviderCreateSequential but it needs the raw pixels in the constructor...

Right now i am doing something like this :

UIImage* srcImage = ...;
    CFDataRef cgImgDataRef = CGDataProviderCopyData(CGImageGetDataProvider(srcImage.CGImage));//After this call, all pixels are decoded into memory and the app crashes
char* imageData = (char*)CFDataGetBytePtr(cgImgDataRef);

Answer 1

The only possible way this might work is if you create an CGImageSourceCreateWithData() (or URL whatever), then create a CGImageRef using CGImageCreateWithJPEGDataProvider or CGImageCreateWithPNGDataProvider. With that CGImageRef, you could TRY to use CGImageCreateWithImageInRect() and pull a subsection of the big image out.

If what you are trying to do is tile the image please clarify your question as I would have more information for you then.