Question

I can’t figure out how i can save my drawn path to an UIImage?
I know that I have to use UIGraphicsBeginImageContext and something like [drawImage drawInRect:CGRectMake(0, 0, drawImage.size.width, drawImage.size.height)];
But I don’t know where to put it in my touch functions.

I need to save every path to the image, because I want to be able to change the color and alpha values after each drawn line.
With this code, all the lines will be adjusted in color and width at the same time when I change the values.

- (id) initWithFrame:(CGRect)frame andImage: (UIImageView*) image
{
    ...
    paths = [[NSMutableArray alloc]init];

    drawImage = image;
    self.backgroundColor=[UIColor clearColor];
    [self addSubview:drawImage];
}
- (void)drawRect:(CGRect)rect
{
    [brushPattern setStroke];
    [myPath strokeWithBlendMode:kCGBlendModeNormal alpha:1.0];
    // Drawing code
    //[myPath stroke];
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *mytouch=[[touches allObjects] objectAtIndex:0];
    myPath=[[UIBezierPath alloc]init];
    [myPath moveToPoint:[mytouch locationInView:self]];
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *mytouch=[[touches allObjects] objectAtIndex:0];
    [myPath addLineToPoint:[mytouch locationInView:self]];
    [self setNeedsDisplay];
}

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

    [paths addObject:myPath];
    [myPath release];
}

Answer 1

Based on your earlier question, I am assuming that the image view is a subview of this custom view object. You will need to maintain a mutable array of paths in this class. Initialize it at touchesBegan:withEvent: and close the path at touchesEnded:withEvent:. Push the path into the array. At every touch event (began, moved, ended), call a method that updates the image view’s image after adding the touch point to the path.

Updating the image will involve creating an empty image context and then iterating over all paths in your array and the current path while stroking them. Once you’re done drawing, generate the image object from the context and set it to the image. Pretty straightforward until we notice that each path might differ in attributes. To deal with this you should create a container class for the path which will hold the attributes about the path. Push an object of this class for every path into the array rather than the path itself. This way you can maintain state for your view.