图片削减

UIImage+Crop.h

#import <UIKit/UIKit.h>

@interface UIImage (Crop)

- (UIImage *)imageByScalingAndCroppingForSize:(CGSize)targetSize;

@end

UIImage+Crop.m

#import "UIImage+Crop.h"

@implementation UIImage (Crop)

- (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 = heightFactor; 
        else
            scaleFactor = widthFactor;
        
        scaledWidth = width * scaleFactor;
        scaledHeight = height * scaleFactor;
        
        if (widthFactor > heightFactor) {
            thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
        } else if (widthFactor < heightFactor) {
            thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
        }
    } 
    
    CGSize target_size = CGSizeMake(scaledWidth, scaledHeight);
    UIGraphicsBeginImageContext(target_size); 
    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width = scaledWidth;
    thumbnailRect.size.height = scaledHeight;    
    [sourceImage drawInRect:thumbnailRect];
    
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return newImage;
}

@end