iOS : 在 CGContext 上绘图最终会模糊
iOS : Drawing on a CGContext eventually blurs
我有一个显示文档的应用程序,该文档顶部有一个 UIImage,您可以在其中绘制线条等以突出显示内容。
如果我一直画线(触摸、画、抬起手指,然后在屏幕的不同区域重复)
线条慢慢模糊。
这是我的触摸代码,我使用 kCGBlendModeCopy 作为混合模式,但使用了 kCGBlendModeNormal。 DrawingView 是一个 UIImageView。
更新
这是我已经画过的线,它们越旧越模糊,感觉每增加一条线都会衰减旧线。在 iPad 2 ios8 iPad Mini Retina ios7
上测试
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = NO;
if ( self.drawingEnabled )
{
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self.drawingView];
UIGraphicsBeginImageContext(self.drawingView.frame.size);
[self.drawingView.image drawInRect:CGRectMake(0, 0, self.drawingView.frame.size.width, self.drawingView.frame.size.height) blendMode:kCGBlendModeCopy alpha:1.0];
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
if ( self.drawingEnabled )
{
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.drawingView];
CGContextRef ctxt = UIGraphicsGetCurrentContext();
CGContextMoveToPoint(ctxt, lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(ctxt, currentPoint.x, currentPoint.y);
CGContextSetLineCap(ctxt, kCGLineCapRound);
CGContextSetLineWidth(ctxt, self.brush );
CGContextSetRGBStrokeColor(ctxt, self.redColour, self.greenColour, self.blueColour, OPACITY);
if (self.eraserOn)
{
CGContextSetBlendMode(ctxt,kCGBlendModeClear);
}
else
{
CGContextSetBlendMode(ctxt,kCGBlendModeCopy);
}
CGContextStrokePath(ctxt);
self.drawingView.image = UIGraphicsGetImageFromCurrentImageContext();
lastPoint = currentPoint;
}
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[super touchesCancelled:touches withEvent:event];
UIGraphicsEndImageContext();
if(!mouseSwiped)
{
//self.drawingView.image = nil;
}
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
if ( self.drawingEnabled )
{
if(!mouseSwiped) {
UIGraphicsEndImageContext();
UIGraphicsBeginImageContext(self.drawingView.frame.size);
[self.drawingView.image drawInRect:CGRectMake(0, 0, self.drawingView.frame.size.width, self.drawingView.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), self.brush);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), self.redColour, self.greenColour, self.blueColour, OPACITY);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
self.drawingView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
if (self.delegate)
{
[self.delegate drawingUpated];
}
//NSLog(@"%@ --- %@", NSStringFromCGRect(self.frame) , NSStringFromCGRect(self.drawingView.frame) );
}
}
这原来是我如何设置自我框架的问题。 drawingView和里面图片的大小。
图像为 1005 x 720
drawingView 为 1004.2 x 719.9,因此存在舍入问题。每次我画一条新线时,它都会向下舍入。
我有一个显示文档的应用程序,该文档顶部有一个 UIImage,您可以在其中绘制线条等以突出显示内容。
如果我一直画线(触摸、画、抬起手指,然后在屏幕的不同区域重复)
线条慢慢模糊。
这是我的触摸代码,我使用 kCGBlendModeCopy 作为混合模式,但使用了 kCGBlendModeNormal。 DrawingView 是一个 UIImageView。
更新 这是我已经画过的线,它们越旧越模糊,感觉每增加一条线都会衰减旧线。在 iPad 2 ios8 iPad Mini Retina ios7
上测试- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = NO;
if ( self.drawingEnabled )
{
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self.drawingView];
UIGraphicsBeginImageContext(self.drawingView.frame.size);
[self.drawingView.image drawInRect:CGRectMake(0, 0, self.drawingView.frame.size.width, self.drawingView.frame.size.height) blendMode:kCGBlendModeCopy alpha:1.0];
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
if ( self.drawingEnabled )
{
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.drawingView];
CGContextRef ctxt = UIGraphicsGetCurrentContext();
CGContextMoveToPoint(ctxt, lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(ctxt, currentPoint.x, currentPoint.y);
CGContextSetLineCap(ctxt, kCGLineCapRound);
CGContextSetLineWidth(ctxt, self.brush );
CGContextSetRGBStrokeColor(ctxt, self.redColour, self.greenColour, self.blueColour, OPACITY);
if (self.eraserOn)
{
CGContextSetBlendMode(ctxt,kCGBlendModeClear);
}
else
{
CGContextSetBlendMode(ctxt,kCGBlendModeCopy);
}
CGContextStrokePath(ctxt);
self.drawingView.image = UIGraphicsGetImageFromCurrentImageContext();
lastPoint = currentPoint;
}
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[super touchesCancelled:touches withEvent:event];
UIGraphicsEndImageContext();
if(!mouseSwiped)
{
//self.drawingView.image = nil;
}
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
if ( self.drawingEnabled )
{
if(!mouseSwiped) {
UIGraphicsEndImageContext();
UIGraphicsBeginImageContext(self.drawingView.frame.size);
[self.drawingView.image drawInRect:CGRectMake(0, 0, self.drawingView.frame.size.width, self.drawingView.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), self.brush);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), self.redColour, self.greenColour, self.blueColour, OPACITY);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
self.drawingView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
if (self.delegate)
{
[self.delegate drawingUpated];
}
//NSLog(@"%@ --- %@", NSStringFromCGRect(self.frame) , NSStringFromCGRect(self.drawingView.frame) );
}
}
这原来是我如何设置自我框架的问题。 drawingView和里面图片的大小。
图像为 1005 x 720 drawingView 为 1004.2 x 719.9,因此存在舍入问题。每次我画一条新线时,它都会向下舍入。