我不想要一个在其他部分是半透明而在中间完全透明的图像视图.. 看这张图片..
我已经做到了,但这不是最好的方法..我只能在黄线内有一个透明的矩形吗...?
编辑:是否可以更改视图的某个矩形的 alpha ..?
我不想要一个在其他部分是半透明而在中间完全透明的图像视图.. 看这张图片..
我已经做到了,但这不是最好的方法..我只能在黄线内有一个透明的矩形吗...?
编辑:是否可以更改视图的某个矩形的 alpha ..?
将自定义 UIView 放置在显示图像、大小和位置的视图上以完全重叠。在自定义视图的 drawRect 方法中
- (void)drawRect:(CGRect)rect
{
// Drawing code
CGRect rBounds = self.bounds;
CGContextRef context = UIGraphicsGetCurrentContext();
// Fill background with 80% white
CGContextSetFillColorWithColor(context, [[[UIColor whiteColor] colorWithAlphaComponent:0.8] CGColor]);
CGContextFillRect(context, rBounds);
// Draw the window 'frame'
CGContextSetStrokeColorWithColor(context, [[UIColor orangeColor] CGColor]);
CGContextSetLineWidth(context, 10);
CGContextStrokeRect(context, self.maskRect);
// make the window transparent
CGContextSetBlendMode(context, kCGBlendModeClear);
CGContextFillRect(context, self.maskRect);
}
其中 maskRect 是要显示为透明的矩形。确保自定义视图的背景颜色设置为“clearColor”
您可以编写更改 maskRect 所需的任何附加逻辑并在此视图上调用“setNeedsDisplay”。
经过大量的努力,我找到了解决方案。
这是它的代码!
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
[screenShotButton setHidden:YES];
UITouch *touch = [touches anyObject];
CGPoint pnt =[touch locationInView:self.view];
CGRect viewFrame=changeView.frame;
CGFloat x1Diff,y1Diff,x2Diff,y2Diff;
x1Diff=ABS(viewFrame.origin.x-pnt.x);
y1Diff=ABS(viewFrame.origin.y-pnt.y);
x2Diff=ABS(viewFrame.origin.x+viewFrame.size.width-pnt.x);
y2Diff=ABS(viewFrame.origin.y+viewFrame.size.height-pnt.y);
if (x1Diff<=10) {
left=YES;
shouldExpand=YES;
}
if (y1Diff<10) {
top=YES;
shouldExpand=YES;
}
if (x2Diff<=10) {
right=YES;
shouldExpand=YES;
}
if (y2Diff<=10) {
bottom=YES;
shouldExpand=YES;
}
if(CGRectContainsPoint(changeView.frame, pnt))
{
shouldChange=YES;
fromPoint=pnt;
}
else
{
shouldChange=NO;
}
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
if (!shouldChange) {
return;
}
if (shouldExpand)
{
UITouch *touch = [touches anyObject];
CGPoint pnt =[touch locationInView:self.view];
CGRect preFram =changeView.frame;
CGRect modifiedFrame=preFram;
if (left) {
modifiedFrame.origin.x=preFram.origin.x-(fromPoint.x-pnt.x);
modifiedFrame.size.width=preFram.size.width+fromPoint.x-pnt.x;
fromPoint.x=pnt.x;
}
if (right) {
modifiedFrame.size.width=preFram.size.width+pnt.x-fromPoint.x;
fromPoint.x=pnt.x;
}
if (top) {
modifiedFrame.origin.y=preFram.origin.y-(fromPoint.y-pnt.y);
modifiedFrame.size.height=preFram.size.height+fromPoint.y-pnt.y;
fromPoint.y=pnt.y;
}
if (bottom) {
modifiedFrame.size.height=preFram.size.height+pnt.y-fromPoint.y;
fromPoint.y=pnt.y;
}
changeView.frame=modifiedFrame;
[clearImage setBounds:CGRectMake(0-modifiedFrame.origin.x, 0-modifiedFrame.origin.y, clearImage.frame.size.width, clearImage.frame.size.height)];
}
else
{
UITouch *touch = [touches anyObject];
CGPoint pnt =[touch locationInView:self.view];
changeView.center=CGPointMake(changeView.center.x-fromPoint.x+pnt.x, changeView.center.y-fromPoint.y+pnt.y);
[clearImage setBounds:CGRectMake(0-changeView.frame.origin.x, 0-changeView.frame.origin.y, clearImage.frame.size.width, clearImage.frame.size.height)];
fromPoint=pnt;
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[screenShotButton setHidden:NO];
left=top=right=bottom=NO;
shouldExpand=NO;
fromPoint=CGPointZero;
toPoint=CGPointZero;
shouldChange=NO;
}
- (IBAction)takeScreenShot:(id)sender
{
[screenShotButton setHidden:YES];
UIGraphicsBeginImageContext(self.view.frame.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextScaleCTM(context, 1.0, 1.0);
[self.view.layer renderInContext:context];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *filePath = [NSString stringWithFormat:@"%@/1.png",docPath];
CGRect cutRect = changeView.frame;
CGImageRef imgRef = CGImageCreateWithImageInRect([img CGImage], cutRect);
CFURLRef url = (__bridge CFURLRef)[NSURL fileURLWithPath:filePath];
CGImageDestinationRef destination = CGImageDestinationCreateWithURL(url, kUTTypePNG, 1, NULL);
CGImageDestinationAddImage(destination, imgRef, nil);
CFRelease(imgRef);
if (!CGImageDestinationFinalize(destination)) {
NSLog(@"Failed to write image to %@", filePath);
}
img=nil;
imgRef=nil;
CFRelease(destination);
[screenShotButton setHidden:NO];
[changeView setHidden:NO];
}
只是,这里的逻辑很重要!!
你为什么不这样做:
一个简单的方法
1:Create a image in photoshop with the alpha values which you have specified.
2:Place the new imageview over your image .
3:If you want to move the transparent box ,change the image frame.
4:If you want to expand you just change the size of upper image.
我想你可以使用 CGContext
void CGContextDrawRadialGradient(
CGContextRef context,
CGGradientRef gradient,
CGPoint startCenter,
CGFloat startRadius,
CGPoint endCenter,
CGFloat endRadius,
CGGradientDrawingOptions options
);
请参阅下面的链接CGContext 参考 或CGGradient 参考
我认为您也许可以更改所选矩形的外部。至于下图,你应该 4 个矩形的 4 个 alpha。例如,首先您设置白色窗口背景颜色,然后将 4 个 alpas 矩形设置为 0.5。
我认为您最好使用 CALayer 而不是 UIView。
我希望我的建议对你有所帮助。