Drawing UIImage into CurrentContext

Question

Hi, in my application i've used a UIImagePickerController to take a photo, and after i took the photo, i cant't draw it using UIImageView because i want draw on it some lines with my finger;

To this end I have written in draw rect methods this code:

• (void)drawRect:(CGRect)rect {

  [self.myimage drawInRect: rect];
  
  
  //Disegno rettangolo del tag
  CGContextRef myContext = UIGraphicsGetCurrentContext();
  
  
  CGContextSetRGBStrokeColor(myContext, 0.5, 0.5, 0.5, 1.0);
  
  
  CGContextSetLineWidth(myContext, 3.0f);
  
  
  CGContextAddPath(myContext, pathTouches);
  
  
  CGContextStrokePath(myContext);
  

  }

and in touchesMoved:

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    UITouch *touch = [touches anyObject];
    CGPoint locationInView = [touch locationInView:self];

    // Draw a connected sequence of line segments
    CGPoint addLines[] =
    {
     //....
            //some lines
    };

    CGMutablePathRef newPath = CGPathCreateMutable();
    CGPathRelease(pathTouches);
    pathTouches = CGPathCreateMutableCopy(newPath);
    CGPathRelease(newPath);

    CGPathAddLines(pathTouches, NULL, addLines, sizeof(addLines)/sizeof(addLines[0]));

    [self setNeedsDisplay];

}

Is correct to call [self setNeedsDisplay]; every time that i move my finger or there is a better way to do this?

thanks

Answer 1

i have done this but stuck at another problem...here is your solution...

- (void)imagePickerController:(UIImagePickerController *)picker 
 didFinishPickingImage:(UIImage *)image
     editingInfo:(NSDictionary *)editingInfo
{
// Dismiss the image selection, hide the picker and
//show the image view with the picked image
[picker dismissModalViewControllerAnimated:YES];
imagePickerController.view.hidden = YES;
[imagePickerController release];
imageView.image = image;
imageView.hidden = NO;
[imageView setFrame:CGRectMake(0, 20, 320, 396)];
[window bringSubviewToFront:imageView];
}

then

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
if ([touch view] == EditImageView)
{
 lastPoint = currentPoint;
 lastPoint = [touch locationInView:self.view];

UIGraphicsBeginImageContext(EditImageView.frame.size);
[EditImageView.image drawInRect:CGRectMake(0, 0, EditImageView.frame.size.width, EditImageView.frame.size.height)];

//sets the style for the endpoints of lines drawn in a graphics context
ctx = UIGraphicsGetCurrentContext();
CGContextSetLineCap(ctx, kCGLineCapRound);
//sets the line width for a graphic context
CGContextSetLineWidth(ctx,10.0);
//set the line colour
CGContextSetRGBStrokeColor(ctx, 1.0, 0.0, 0.0, 1.0);
//creates a new empty path in a graphics context
CGContextBeginPath(ctx);
 CGContextSetAllowsAntialiasing(ctx,TRUE);
//begin a new path at the point you specify
CGContextMoveToPoint(ctx, currentPoint.x, currentPoint.y);
//Appends a straight line segment from the current point to the provided point 
CGContextAddLineToPoint(ctx, lastPoint.x,lastPoint.y);
//paints a line along the current path
CGContextStrokePath(ctx);
EditImageView.image = UIGraphicsGetImageFromCurrentImageContext();
 [EditImageView setNeedsDisplay];

 CGContextSaveGState(ctx);
 UIGraphicsEndImageContext();
  currentPoint = lastPoint;
} 
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject]; 
if ([touch view] == EditImageView)
{
 currentPoint=[touch locationInView:self.view];
}
}

where currentPoint and lastPoint are CGPoint Declared in Header File.