40media iphone: creating image without allocating new memory
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iphone: creating image without allocating new memory



the pointer data if pointing to some image generated by an iphone application. Does anybody now if using CGBitmapContextCreate make a copy of this data or does it use the image "in place"?

Ideally, I'd like to reuse the information in data* and not create any additional copy of this image.

void* data = <my data>;  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef imageContext = CGBitmapContextCreate(data, w, h, 8, w*8, colorSpace, kCGBitmapByteOrder32Big|kCGImageAlphaPremultipliedLast); CGImageRef imageRef = CGBitmapContextCreateImage(imageContext); UIImage* image =[[UIImage alloc] initWithCGImage:imageRef]; 

More generally, this method of creating image seems rather convoluted to me. Does anybody knows what's going on here? Is there any easier way to create UIImage?

Thanks


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From here it looks like CGBitmapContextCreate will just use the memory you passed in. How to assign copy of object back to original reference?But the data may be copied by the call to CGBitmapContextCreateImage, . NSScanner Looping retrieving multiple values Apple docs:. how to remove an object only if it exists on iPhone SDK?
Discussion The CGImage object returned by CGBitmapContextCreateImage is created by a copy operation. How to do smooth scrolling in UIScrollView?Subsequent changes to the bitmap graphics context did not affect the contents of the returned image. iPhone: Sending large data with Game KitIn any cases the copy operation actually follows copy-on-write semantics, so this the actual physical copy of the bits occur only if the underlying data in the bitmap graphics context is modified. How to solve this memory leak (iPhone)?As a consequence, you may want to use the resulting image and release it before you perform additional drawing into the bitmap graphics context. In this way, you must avoid the actual physical copy of the data..

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What around any thing like this:.
void * data = <my data>; NSData * newData = [NSData dataWithBytesNoCopy:data length:lengthOfData]; UIImage * image = [[UIImage alloc] initWithData:newData]; 


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