iphone - 如何裁剪具有固定尺寸的 UIImage？

Question

我有一个尺寸为 (0,0,320,460) 的 uiimage 如何将此图像裁剪为尺寸 (10,30,300,300)

Answer 1

Target size in my code is always set to the full screen size of the device (so you have to change it).

@implementation UIImage (Extras)

    #pragma mark -
    #pragma mark Scale and crop image

    - (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 = widthFactor; // scale to fit height
            }
            else
            {
                scaleFactor = heightFactor; // scale to fit width
            }

            scaledWidth  = width * scaleFactor;
            scaledHeight = height * scaleFactor;

            // center the image
            if (widthFactor > heightFactor)
            {
                thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
            }
            else
            {
                if (widthFactor < heightFactor)
                {
                    thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
                }
            }
        }   

        UIGraphicsBeginImageContext(targetSize); // this will crop

        CGRect thumbnailRect = CGRectZero;
        thumbnailRect.origin = thumbnailPoint;
        thumbnailRect.size.width  = scaledWidth;
        thumbnailRect.size.height = scaledHeight;

        [sourceImage drawInRect:thumbnailRect];

        newImage = UIGraphicsGetImageFromCurrentImageContext();

        if(newImage == nil)
        {
            NSLog(@"could not scale image");
        }

        //pop the context to get back to the default
        UIGraphicsEndImageContext();

        return newImage;
    }