私が行ったアプリで動作させる方法は次のとおりです。
//this is a method that takes a UIImage and slices it into 16 tiles (GridSize * GridSize)
#define GridSize 4
- (void) sliceImage:(UIImage *)image {
CGSize imageSize = [image size];
CGSize square = CGSizeMake(imageSize.width/GridSize, imageSize.height/GridSize);
CGFloat scaleMultiplier = [image scale];
square.width *= scaleMultiplier;
square.height *= scaleMultiplier;
CGFloat scale = ([self frame].size.width/GridSize)/square.width;
CGImageRef source = [image CGImage];
if (source != NULL) {
for (int r = 0; r < GridSize; ++r) {
for (int c = 0; c < GridSize; ++c) {
CGRect slice = CGRectMake(c*square.width, r*square.height, square.width, square.height);
CGImageRef sliceImage = CGImageCreateWithImageInRect(source, slice);
if (sliceImage) {
//we have a tile (as a CGImageRef) from the source image
//do something with it
CFRelease(sliceImage);
}
}
}
}
}
トリックは、-[UIImage scale]
プロパティを使用して、スライスする必要がある四角形の大きさを把握することです。