Core Graphics drawing a bitmap

(Don Giovanni) #1

Hello All.

I'm trying to use Core Graphics to draw to a UIView. I'm purposely avoiding using UIKit drawing methods for UIView because I'd like to go deeper into drawing: i have a button whose push down implementation in the View Controller is:

let colorSpace = CGColorSpaceCreateDeviceRGB()

a = CGContext(data: nil, width: 100, height: 100, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo:
    a?.setFillColor(red: 1.0, green: 0.0, blue: 0.0, alpha: 0.0);
    a?.fill(CGRect(x: 0, y: 0, width: 100, height: 100));

    let i = a?.makeImage();

    let v1 = DGView(frame: CGRect(x: 0, y: 0, width: 500, height: 550));
    v1.tag = 100;
    v1.image = UIImage(cgImage: i!);
    self.view.viewWithTag(100)?.backgroundColor = UIColor.white;

when i push the button, a UIView subclass (DGView) pops up with white
  background. in the draw method of DGView, I added this code:

    let c = UIGraphicsGetCurrentContext();
    c?.draw((c?.makeImage())!, in: CGRect(x: 0, y: 0, width: 100, height:


The problem is nothing is being drawn. Output should've been a red rectangle. I would really appreciate some guidance on this. Thanks.

(Quinn “The Eskimo!”) #2

swift-users isn’t really the right place for questions related to Apple frameworks. You might be better off asking this in a different context, such as the Cocoa Touch topic area on DevForums.


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On 23 Apr 2017, at 06:11, Don Giovanni via swift-users <> wrote:

I'm trying to use Core Graphics to draw to a UIView.

Quinn "The Eskimo!" <>
Apple Developer Relations, Developer Technical Support, Core OS/Hardware