[IPhone] 如何缩小UIImage

这段代码示范如何缩小UIImage

 

@implementation UIImage (Extras)#pragma mark -#pragma mark Scale and crop image- (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize{UIImage *sourceImage = self;UIImage *newImage = nil; CGSize imageSize = sourceImage.size;CGFloat width = imageSize.width;CGFloat height = imageSize.height;CGFloat targetWidth = targetSize.width;CGFloat targetHeight = targetSize.height;CGFloat scaleFactor = 0.0;CGFloat scaledWidth = targetWidth;CGFloat scaledHeight = targetHeight;CGPoint thumbnailPoint = CGPointMake(0.0,0.0);if (CGSizeEqualToSize(imageSize, targetSize) == NO) { CGFloat widthFactor = targetWidth / width; CGFloat heightFactor = targetHeight / height; if (widthFactor > heightFactor) scaleFactor = widthFactor; // scale to fit height else scaleFactor = heightFactor; // scale to fit width scaledWidth = width * scaleFactor; scaledHeight = height * scaleFactor; // center the image if (widthFactor > heightFactor) { thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; } else if (widthFactor < heightFactor) { thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5; } } UIGraphicsBeginImageContext(targetSize); // this will cropCGRect thumbnailRect = CGRectZero;thumbnailRect.origin = thumbnailPoint;thumbnailRect.size.width = scaledWidth;thumbnailRect.size.height = scaledHeight;[sourceImage drawInRect:thumbnailRect];newImage = UIGraphicsGetImageFromCurrentImageContext();if(newImage == nil) NSLog(@"could not scale image");//pop the context to get back to the defaultUIGraphicsEndImageContext();return newImage;}