UIImage分类,用于图片缩放 Note: 处理大分辨率图片时,往往容易出现OOM,原因是-[UIImage drawInRect:]在绘制时,先解码图片,再生成原始分辨率大小的bitmap,这是很耗内存的。解决方法是使用更低层的ImageIO接口,避免中间bitmap产生
- (UIImage *)scaleImage:(UIImage *)image newSize:(CGSize)newSize {
UIGraphicsBeginImageContextWithOptions(newSize, NO, 0);
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
+ (UIImage *)scaledImageWithData:(NSData *)data withSize:(CGSize)size scale:(CGFloat)scale orientation:(UIImageOrientation)orientation {
CGFloat maxPixelSize = MAX(size.width, size.height);
CGImageSourceRef sourceRef = CGImageSourceCreateWithData((__bridge CFDataRef)data, nil);
NSDictionary *options = @{(__bridge id)kCGImageSourceCreateThumbnailFromImageAlways: (__bridge id)kCFBooleanTrue,
(__bridge id)kCGImageSourceThumbnailMaxPixelSize: [NSNumber numberWithFloat:maxPixelSize]};
CGImageRef imageRef = CGImageSourceCreateImageAtIndex(sourceRef, 0, (__bridge CFDictionaryRef)options);
UIImage *resultImage = [UIImage imageWithCGImage:imageRef scale:scale orientation:orientation];
CGImageRelease(imageRef);
CFRelease(sourceRef);
return resultImage;
}