Syntax

$canvasGrayscale

Parameters

None. The engine accepts one optional argument and ignores it.

Return value

An empty string. The effect is recorded for the current canvas (the last one made with $canvasCreate) and applied, in order, when the canvas is rendered.

Behavior

• Each pixel of the canvas is converted to a shade of gray from a weighted sum of its channels: in tests #FF0000 gives gray 76, #00FF00 gives 149, #0000FF gives 29 and white stays white (about 30% red, 59% green, 11% blue).
• It applies to the whole canvas at the point where it is written: only the operations written before it are affected.
• It cannot be undone.

Examples

Simple conversion to black and white

$canvasCreate[photo;400;400]
$canvasLoadImage[https://example.com/photo.png;0;0;400;400]
$canvasGrayscale
$attachImage[photo]
$sendMessage[🎨 Image converted to grayscale!]

Grayscale then invert

$canvasCreate[photo;400;400]
$canvasLoadImage[https://example.com/photo.png;0;0;400;400]
$canvasGrayscale
$canvasInvert
$attachImage[photo]
$sendMessage[🕰️ Negative effect applied!]

Before/After comparison

$canvasCreate[before;400;400]
$canvasLoadImage[https://example.com/photo.png;0;0;400;400]
$canvasCreate[after;400;400]
$canvasLoadImage[https://example.com/photo.png;0;0;400;400]
$canvasGrayscale
$attachImage[before]
$attachImage[after]
$sendMessage[⚫ Original vs Grayscale:]

Notes

• A canvas must have been created with $canvasCreate[] first; otherwise the call has no effect.
• $canvasLoadImage[url;0;0;width;height] draws the image over the canvas, so the grayscale then covers it.
• To invert the colors, use $canvasInvert instead.
• For rotation, use $canvasRotate[degrees].