裁剪并获取固定大小的图片

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//转换图片大小 - (UIImage *)reSizeImage:(UIImage *)image toSize:(CGSize)reSize   {     UIGraphicsBeginImageContext(CGSizeMake(reSize.width, reSize.height));     [image drawInRect:CGRectMake(0, 0, reSize.width, reSize.height)];     UIImage *reSizeImage = UIGraphicsGetImageFromCurrentImageContext();     UIGraphicsEndImageContext();           return reSizeImage;       }   //规格化图片并转换为指定大小 - (UIImage *)squareImageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {     double ratio;     double delta;     CGPoint offset;           //make a new square size, that is the resized imaged width     CGSize sz = CGSizeMake(newSize.width, newSize.width);           //figure out if the picture is landscape or portrait, then     //calculate scale factor and offset     if (image.size.width > image.size.height) {         ratio = newSize.width / image.size.width;         delta = (ratio*image.size.width - ratio*image.size.height);         offset = CGPointMake(delta/2, 0);     } else {         ratio = newSize.width / image.size.height;         delta = (ratio*image.size.height - ratio*image.size.width);         offset = CGPointMake(0, delta/2);     }           //make the final clipping rect based on the calculated values     CGRect clipRect = CGRectMake(-offset.x, -offset.y,                                  (ratio * image.size.width) + delta,                                  (ratio * image.size.height) + delta);                 //start a new context, with scale factor 0.0 so retina displays get     //high quality image     if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {         UIGraphicsBeginImageContextWithOptions(sz, YES, 0.0);     } else {         UIGraphicsBeginImageContext(sz);     }     UIRectClip(clipRect);     [image drawInRect:clipRect];     UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();     UIGraphicsEndImageContext();           return newImage; }