I'm drawing a graph in Canvas and struggling with the fact that the y-axis is "backward." The origin is in the top-left corner, and increasing values go down rather than up.
(0,0) (x,0) (0,y) ^
+--------------> |
| |
| CANVAS | INSTEAD
| DOES THIS | OF THIS
| |
| +----------------->
(0,y) v (0,0) (x,0)
I know that I can move the origin to the bottom-left corner using translate().
context.translate(0, canvas.height);
And I know that I can invert the y-axis using scale().
context.scale(1, -1);
That seems to work, except that it causes text to appear upside-down. Is there a way to make Canvas's coordinates work the way I expect?
For more modern setup, you can use context.transform(1, 0, 0, -1, 0, canvas.height)
. This flips y axis and moves the whole canvas one screenful.
More on available transformations: https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/transform