我使用 NSAffineTransform 类在其中心旋转了一个 NSImage 并且它可以工作。代码在这里:
- (NSImage*)rotateImage: (NSImage*)myImage angle:(float)rotateAngle {
NSRect imageBounds = {NSZeroPoint, [myImage size]};
NSRect transformedImageBounds = imageBounds;
NSBezierPath* boundsPath = [NSBezierPath bezierPathWithRect:imageBounds];
NSAffineTransform* transform = [NSAffineTransform transform];
// calculate the bounds for the rotated image
if (rotateAngle != 0) {
NSAffineTransform* temptransform = [NSAffineTransform transform];
[temptransform rotateByDegrees:rotateAngle];
[boundsPath transformUsingAffineTransform:temptransform];
NSRect rotatedBounds = {NSZeroPoint, [boundsPath bounds].size};
// center the image within the rotated bounds
imageBounds.origin.x += (NSWidth(rotatedBounds) - NSWidth (imageBounds))/2;
imageBounds.origin.y += (NSHeight(rotatedBounds) - NSHeight (imageBounds))/2;
// set up the rotation transform
[transform translateXBy:+(NSWidth(rotatedBounds) / 2) yBy:+ (NSHeight(rotatedBounds) / 2)];
[transform rotateByDegrees:rotateAngle];
[transform translateXBy:-(NSWidth(rotatedBounds) / 2) yBy:- (NSHeight(rotatedBounds) / 2)];
transformedImageBounds = rotatedBounds;
}
// draw the original image into the new image
NSImage* transformedImage = [[NSImage alloc] initWithSize:transformedImageBounds.size];;
[transformedImage lockFocus];
[transform concat];
[myImage drawInRect:imageBounds fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0] ;
[transformedImage unlockFocus];
return transformedImage;
}
但是生成的图像质量很差。如何解决?
有人说“lockFocus”方法导致了这种情况,但我不知道如何在不使用该方法的情况下做到这一点。