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UIImageView で画像の上に描画するのに問題があります。既に「UIImage に別の画像を描画する」を見てきましたが、それは非常に役に立ちました。これが私のシナリオです: UITableView を含む UIPopoverController があり、ユーザーがスクロール可能なテーブル ビューの下部にいるときに上向きの三角形を表示したいと考えています。

私のコード:

- (UIImage *) drawTriangleInViewForSize:(CGSize)sizeOfView
                     imageToDrawOn:(UIImage *)underImage
                           isAtTop:(BOOL)top{
CGPoint firstPoint;
CGPoint secondPoint;
CGPoint thirdPoint;

if(!top){
 //I want to draw a equilateral triangle (side length 10) in the center of the image in
 //the imageView, these are the coordinates I am using.
    firstPoint = CGPointMake(underImage.size.width * 0.5 + 5, underImage.size.height * 0.5 - 5);
    secondPoint = CGPointMake((firstPoint.x - 10), firstPoint.y);
    thirdPoint = CGPointMake(underImage.size.width * 0.5,
                             underImage.size.width * 0.5 + 5);

}
*/
**DISREGARD**
else{
    firstPoint = CGPointMake(sizeOfView.width * 0.5 + 5,
                             self.tableViewChoices.rowHeight * 0.5 - 5);
    secondPoint = CGPointMake((firstPoint.x - 10), firstPoint.y);
    thirdPoint = CGPointMake(sizeOfView.width * 0.5,
                             self.tableViewChoices.rowHeight * 0.5 + 5);
}*/
//get the size of the image for the drawInRect: method
CGFloat imageViewWidth = sizeOfView.width;
CGFloat imageViewHeight = self.tableViewChoices.rowHeight;

//set the graphics context to be the size of the image
UIGraphicsBeginImageContextWithOptions(underImage.size, YES, 0.0);

[underImage drawInRect:CGRectMake(0.0, 0.0, imageViewWidth, imageViewHeight)];

//set the line attributes
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(ctx, [UIColor blackColor].CGColor);
CGContextSetFillColorWithColor(ctx, [UIColor clearColor].CGColor);
CGContextSetLineWidth(ctx, 0.05);

UIGraphicsPushContext(ctx);
    //draw the triangle
CGContextBeginPath(ctx);
CGContextMoveToPoint(ctx, firstPoint.x, firstPoint.y);
CGContextAddLineToPoint(ctx, secondPoint.x, secondPoint.y);
CGContextAddLineToPoint(ctx, thirdPoint.x, thirdPoint.y);
CGContextAddLineToPoint(ctx, firstPoint.x, firstPoint.y);
CGContextClosePath(ctx);

UIGraphicsPopContext();

//get the image
UIImage *rslt = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return rslt;
}

imageView の UIImage に三角形を描画するようには見えません。最終結果は、完全に黒い ImageView (UIImage は単なる white.png です)、または imageview の上部にある 1 行です (状況によって異なります)。drawInRect:またはdrawAtPoint:、どの座標を使用するか) 。私がする必要があるのは、上向きの三角形を描くことだけです。難しいことではありません。実際に「本に従って」やっているように見えます。

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2 に答える 2

2

UIImageView の UIImage に三角形を描画する完成したコードを次に示します。

//draws triangle up or down on a UIImage.
+(UIImage *) drawTriangleInViewForSize:(CGSize)sizeOfView
                     imageToDrawOn:(UIImage *)underImage
                           isAtTop:(BOOL)top
{
CGFloat rowHeight = underImage.size.height; //44; //self.tableViewChoices.rowHeight;
CGPoint firstPoint;
CGPoint secondPoint;
CGPoint thirdPoint;

CGFloat imageViewWidth = sizeOfView.width;
CGFloat imageViewHeight = rowHeight;


if(!top){
    //draw a upward facing triangle in the center of the view.
    firstPoint = CGPointMake(imageViewWidth * 0.5 + 15, imageViewHeight * 0.5 - 5);
    secondPoint = CGPointMake((firstPoint.x - 30), firstPoint.y);
    thirdPoint = CGPointMake(imageViewWidth * 0.5,
                             imageViewHeight * 0.5 + 5);

}else{
    //disregard this 'else'
    firstPoint = CGPointMake(sizeOfView.width * 0.5 + 15,
                             rowHeight * 0.5 - 5);
    secondPoint = CGPointMake((firstPoint.x - 10), firstPoint.y);
    thirdPoint = CGPointMake(sizeOfView.width * 0.5,
                             rowHeight * 0.5 + 5);

}


//get the image context with options(recommended funct to use)
//get the size of the imageView
UIGraphicsBeginImageContextWithOptions(CGSizeMake(imageViewWidth, imageViewHeight), YES, 0.0);

//use the the image that is going to be drawn on as the receiver
[underImage drawInRect:CGRectMake(0.0, 0.0, imageViewWidth, imageViewHeight)];



CGContextRef ctx = UIGraphicsGetCurrentContext();

CGContextSetLineWidth(ctx, 0.5);

//UIGraphicsPushContext(ctx);

//uses path ref
CGMutablePathRef path = CGPathCreateMutable();
//draw the triangle
CGPathMoveToPoint(path, NULL, firstPoint.x, firstPoint.y);
CGPathAddLineToPoint(path, NULL, secondPoint.x, secondPoint.y);
CGPathAddLineToPoint(path, NULL, thirdPoint.x, thirdPoint.y);
CGPathAddLineToPoint(path, NULL, firstPoint.x, firstPoint.y);
//close the path
CGPathCloseSubpath(path);
//add the path to the context
CGContextAddPath(ctx, path);
CGContextSetFillColorWithColor(ctx, [UIColor whiteColor].CGColor);
CGContextSetStrokeColorWithColor(ctx, [UIColor blackColor].CGColor);
CGContextFillPath(ctx);
CGContextAddPath(ctx, path);
CGContextStrokePath(ctx);
CGPathRelease(path);

//UIGraphicsPopContext();

//get the new image with the triangle
UIImage *rslt = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return rslt;

}
于 2013-07-29T05:35:10.947 に答える