IOS Create Mask on an image using drawrect - ios

Question

I have created a function to draw a line graph, how can I use the line graph as a mask and put it on top of an image? the image have different color on different height, so what i wanna do is after masking with the line graph, the line graph will display different color on different level. Many thanks for helping me out :)
- (void)drawLineGraphWithContext:(CGContextRef)ctx
{
CGContextSetLineWidth(ctx, 2.0);
CGContextSetStrokeColorWithColor(ctx, [[UIColor colorWithRed:1.0 green:0.5 blue:0 alpha:1.0] CGColor]);
int maxGraphHeight = kGraphHeight - kOffsetY;
CGContextBeginPath(ctx);
CGContextMoveToPoint(ctx, kOffsetX, kGraphHeight - maxGraphHeight * data[0]);
for (int i = 1; i < sizeof(data); i++)
{
CGContextAddLineToPoint(ctx, kOffsetX + i * kStepX, kGraphHeight - maxGraphHeight * data[i]);
}
CGContextDrawPath(ctx, kCGPathStroke);
CGContextSetFillColorWithColor(ctx, [[UIColor colorWithRed:1.0 green:0.5 blue:0 alpha:1.0] CGColor]);
for (int i = 0; i < sizeof(data) - 1; i++)
{
float x = kOffsetX + i * kStepX;
float y = kGraphHeight - maxGraphHeight * data[i];
CGRect rect = CGRectMake(x - kCircleRadius, y - kCircleRadius, 2 * kCircleRadius, 2 * kCircleRadius);
CGContextAddEllipseInRect(ctx, rect);
}
CGContextDrawPath(ctx, kCGPathFillStroke);
CGPathRef myPath = CGContextCopyPath(ctx);
CAShapeLayer *shapeLayer = [[CAShapeLayer alloc] init];
CGPathRef myPath = CGContextCopyPath(ctx);
shapeLayer.path = myPath;
_imageView.layer.mask = shapeLayer;
}

Answer 1

Try to do it this way.
1. Put the Image into an ImageView.
2. Since you already have the Path. And rite now, you will get the last
point as `path.currentPoint`. Add a Line to the `bottomRight` then
to `bottomLeft` and then to the `startingPoint` of the Path. You
will need to store the FirstPoint of the Path Somewhere for this.
Also, all the Path drawing should be in reference to the `bounds` of
the ImageView.
3. Create a CAShapeLayer with the path above. `shapeLayer.path = path`.
4. Set it as mask of the imageView -- imageView.mask = shapeLayer`.
Try it out this way. Cheers, have fun.