[英]Clip UIImage to UIBezierPath (not masking)
我正在尝试基于给定的UIBezierPath
剪辑UIImage
,但生成的图像保留原始形状和大小。 我希望形状和大小类似于路径,即新图像的可见内容。
看看下面这个例子:
以下是我用于在给定路径的情况下屏蔽图像的代码:
func imageByApplyingClippingBezierPath(_ path: UIBezierPath) -> UIImage {
UIGraphicsBeginImageContextWithOptions(CGSize(
width: size.width,
height: size.height
), false, 0.0)
let context = UIGraphicsGetCurrentContext()!
context.saveGState()
path.addClip()
draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
let newImage = UIGraphicsGetImageFromCurrentImageContext()!
context.restoreGState()
UIGraphicsEndImageContext()
return newImage
}
一种解决方案是在屏蔽后对图像进行裁剪,但理想情况下,我希望一次完成尽可能简单有效的图像。
任何解决方案/提示将不胜感激。
感谢Rob,我能够使用CGImage
的cropping(to:)
方法实现解决方案。
这是一个两步过程,首先使用给定路径屏蔽图像,然后使用路径的边界裁剪结果。
以下是我实现剪辑 UIBezierPath
UIImage
扩展的最终工作源代码:
extension UIImage {
func imageByApplyingClippingBezierPath(_ path: UIBezierPath) -> UIImage {
// Mask image using path
let maskedImage = imageByApplyingMaskingBezierPath(path)
// Crop image to frame of path
let croppedImage = UIImage(cgImage: maskedImage.cgImage!.cropping(to: path.bounds)!)
return croppedImage
}
func imageByApplyingMaskingBezierPath(_ path: UIBezierPath) -> UIImage {
// Define graphic context (canvas) to paint on
UIGraphicsBeginImageContext(size)
let context = UIGraphicsGetCurrentContext()!
context.saveGState()
// Set the clipping mask
path.addClip()
draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
let maskedImage = UIGraphicsGetImageFromCurrentImageContext()!
// Restore previous drawing context
context.restoreGState()
UIGraphicsEndImageContext()
return maskedImage
}
}
我在目标C中使用以下内容,用于将任何图像裁剪为非透明矩形。 检查它是否有用
@implementation UIImage (cropTransperant)
- (UIImage *) CropimageByTrimmingTransparentPixels {
int rows = self.size.height;
int cols = self.size.width;
int bytesPerRow = cols*sizeof(uint8_t);
if ( rows < 2 || cols < 2 ) {
return self;
}
uint8_t *bitmapData = calloc(rows*cols, sizeof(uint8_t));
CGContextRef contextRef = CGBitmapContextCreate(bitmapData, cols, rows, 8, bytesPerRow, NULL, kCGImageAlphaOnly);
CGImageRef cgImage = self.CGImage;
CGRect rect = CGRectMake(0, 0, cols, rows);
CGContextDrawImage(contextRef, rect, cgImage);
//get all non-transparent pixels in every row and every column
uint16_t *rowSum = calloc(rows, sizeof(uint16_t));
uint16_t *colSum = calloc(cols, sizeof(uint16_t));
//loop through all pixels
for ( int row = 0; row < rows; row++) {
for ( int col = 0; col < cols; col++)
{
if ( bitmapData[row*bytesPerRow + col] ) { //when you get non transperant pixel
rowSum[row]++;
colSum[col]++;
}
}
}
UIEdgeInsets crop = UIEdgeInsetsMake(0, 0, 0, 0); //croprect, initialize with 0,0,0,
for ( int i = 0; i<rows; i++ ) { //get top
if ( rowSum[i] > 0 ) {
crop.top = i; break;
}
}
for ( int i = rows; i >= 0; i-- ) { //get bottom
if ( rowSum[i] > 0 ) {
crop.bottom = MAX(0, rows-i-1); break;
}
}
for ( int i = 0; i<cols; i++ ) { //get left
if ( colSum[i] > 0 ) {
crop.left = i; break;
}
}
for ( int i = cols; i >= 0; i-- ) { //get right
if ( colSum[i] > 0 ) {
crop.right = MAX(0, cols-i-1); break;
}
}
free(bitmapData);
free(colSum);
free(rowSum);
if ( crop.top == 0 && crop.bottom == 0 && crop.left == 0 && crop.right == 0 ) {
return self;
}
else {
rect.origin.x += crop.left;
rect.origin.y += crop.top;
rect.size.width -= crop.left + crop.right;
rect.size.height -= crop.top + crop.bottom;
//crop image to calcualted rect
CGImageRef newImage = CGImageCreateWithImageInRect(cgImage, rect);
return [UIImage imageWithCGImage:newImage];
}
}
@end
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