V. Castillo V. Castillo - 1 year ago 133
Java Question

What is the best way to read pixels of a JavaFX Canvas?

I want to get the color for specific coordinates inside a

Canvas
. I already tried getting a snapshot using this code:

WritableImage snap = gc.getCanvas().snapshot(null, null);
snap.getPixelReader().getArgb(x, y); //This just gets the color without assigning it.


But it just takes too much time for my application. I was wondering if there is any other way to access the color of a pixel for which I know the coordinates.

Answer Source

A Canvas buffers the drawing instructions prescribed by invoking the methods of a GraphicsContext. There are no pixels to read until the Canvas is rendered in a later pulse, and the internal format of the instruction buffer is not exposed in the API.

As an alternative, consider drawing into a BufferedImage, illustrated here, which allows access to the image's pixels directly and via its WritableRaster. Adding the following line to this complete example outputs the expected value for opaque red in ARGB order: ffff0000.

System.out.println(Integer.toHexString(bi.getRGB(50, 550)));

image

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