//这个方法是把一张UIImage压缩成newSize的尺寸
-(UIImage*)imageWithImageSimple:(UIImage*)image scaledToSize:(CGSize)newSize
{
UIGraphicsBeginImageContext(newSize);
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
/*******截取中间部分*******/
- (UIImage *)scaleImage:(UIImage *)image toScale:(CGSize)reSize
{
//先按要显示的大小去比例缩放下图片，这里压缩成245*245的大小
UIImage *scaledImage = [self imageWithImageSimple:image scaledToSize:CGSizeMake(245, 245)];
//计算截取位置。这里我们考虑一般拍照边界位置可能存在全白或全黑的情况，多数重要的会在中间位置。所以计算下截取是重绘图片的中间位置
float drawW = 0.0;
float drawH = 0.0;
CGSize size_new = scaledImage.size;
if (size_new.width > reSize.width) {
drawW = (size_new.width - reSize.width)/2.0;
}
if (size_new.height > reSize.height) {
drawH = (size_new.height - reSize.height)/2.0;
}
NSLog(@"drawW=====w==%f\n--------drawH==%f\n\n",drawW,drawH);
//截取截取大小为需要显示的大小。取图片中间位置截取
CGRect myImageRect = CGRectMake(drawW, drawH, reSize.width, reSize.height);
UIImage* bigImage= scaledImage;
scaledImage = nil;
CGImageRef imageRef = bigImage.CGImage;
CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef, myImageRect);
UIGraphicsBeginImageContext(reSize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextDrawImage(context, myImageRect, subImageRef);
UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];
UIGraphicsEndImageContext();
CGImageRelease(subImageRef);
return smallImage;
}