IOS开发笔记，对图像的缩放操作

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#pragma mark- 缩放图片按比例+ (UIImage *)scaleImage:(UIImage *)image toScale:(float)scaleSize{    UIGraphicsBeginImageContext(CGSizeMake(image.size.width*scaleSize,image.size.height*scaleSize));    [image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height *scaleSize)];    UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    return scaledImage;}#pragma mark- 缩放图片按大小+ (UIImage *)scaleImage:(UIImage *)image toSize:(CGSize)scaleSize{    UIGraphicsBeginImageContext(scaleSize);    [image drawInRect:CGRectMake(0, 0, scaleSize.width, scaleSize.height)];    UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();    return scaledImage;}#pragma mark- 缩放图片按大小，同时保持比例+ (UIImage *)thumbnailWithImageWithoutScale:(UIImage *)image size:(CGSize)asize{    UIImage *scaleImage;    CGSize newSize = CGSizeMake(96.0, 96.0);    if (nil == image) {        scaleImage = nil;    }        else{                CGSize oldsize = image.size;                CGRect rect;                if (newSize.width/newSize.height > oldsize.width/oldsize.height) {                        rect.size.width = newSize.height*oldsize.width/oldsize.height;                        rect.size.height = newSize.height;                        rect.origin.x = (newSize.width - rect.size.width)/2;                        rect.origin.y = 0;                    }                else{                        rect.size.width = newSize.width;                        rect.size.height = newSize.width*oldsize.height/oldsize.width;                        rect.origin.x = 0;                        rect.origin.y = (newSize.height - rect.size.height)/2;                    }                UIGraphicsBeginImageContext(newSize);                CGContextRef context = UIGraphicsGetCurrentContext();                CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]);                UIRectFill(CGRectMake(0, 0, newSize.width, newSize.height));//clear background                [image drawInRect:rect];                scaleImage = UIGraphicsGetImageFromCurrentImageContext();                UIGraphicsEndImageContext();            }        return scaleImage;}+ (BOOL)checkImageValid:(UIImage *)imageObj{    if (imageObj && imageObj.size.height > 0 && imageObj.size.width > 0)    {        return YES;    }        return NO;}
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