blob: 6626630a3695d2b5f7a1f79e2e3a1702c119e7cc [file] [log] [blame]
<!DOCTYPE html>
<title>Custom Image Upscaling</title>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<script type="text/javascript" src="https://unpkg.com/canvaskit-wasm@0.25.0/bin/full/canvaskit.js"></script>
<style>
figcaption {
max-width: 800px;
}
</style>
<body>
<h1>Custom Image Upscaling</h1>
<div class="slidecontainer">
<input type="range" min="0" max="1" value="0" step="0.01" class="slider" id="sharpen"
title="sharpen coefficient: 0 means nearest neighbor.">
<input type="range" min="0" max="1" value="0.3" step="0.01" class="slider" id="cubic_B"
title="cubic B">
<input type="range" min="0" max="1" value="0.3" step="0.01" class="slider" id="cubic_C"
title="cubic C">
</div>
<figure>
<canvas id=draw width=820 height=820></canvas>
<figcaption>
This demo shows off a custom image upscaling algorithm written in SkSL. The algorithm
can be between nearest neighbor and linear interpolation, depending if the value of the
sharpen (i.e. the first) slider is 0 or 1, respectively. The upper left quadrant shows
the results of a 100x zoom in on a 4 pixel by 4 pixel image of random colors with this
algorithm. The lower left is the same algorithm with a smoothing curve applied.
<br>
For comparison, the upper right shows a stock linear interpolation and the lower right
shows a cubic interpolation with the B and C values controlled by the two remaining
sliders.
</figcaption>
</figure>
</body>
<script type="text/javascript" charset="utf-8">
const ckLoaded = CanvasKitInit({ locateFile: (file) => 'https://unpkg.com/canvaskit-wasm@0.25.0/bin/full/' + file });
ckLoaded.then((CanvasKit) => {
if (!CanvasKit.RuntimeEffect) {
throw 'Need RuntimeEffect';
}
const surface = CanvasKit.MakeCanvasSurface('draw');
if (!surface) {
throw 'Could not make surface';
}
const prog = `
uniform shader image;
uniform float sharp; // 1/m 0 --> NN, 1 --> Linear
uniform float do_smooth; // bool
float2 smooth(float2 t) {
return t * t * (3.0 - 2.0 * t);
}
float2 sharpen(float2 w) {
return saturate(sharp * (w - 0.5) + 0.5);
}
half4 main(float2 p) {
half4 pa = image.eval(float2(p.x-0.5, p.y-0.5));
half4 pb = image.eval(float2(p.x+0.5, p.y-0.5));
half4 pc = image.eval(float2(p.x-0.5, p.y+0.5));
half4 pd = image.eval(float2(p.x+0.5, p.y+0.5));
float2 w = sharpen(fract(p + 0.5));
if (do_smooth > 0) {
w = smooth(w);
}
return mix(mix(pa, pb, w.x), mix(pc, pd, w.x), w.y);
}
`;
const effect = CanvasKit.RuntimeEffect.Make(prog);
const paint = new CanvasKit.Paint();
// image is a 4x4 image of 16 random colors. This very small image will be upscaled
// through various techniques.
const image = function() {
const surf = CanvasKit.MakeSurface(4, 4);
const c = surf.getCanvas();
for (let y = 0; y < 4; y++) {
for (let x = 0; x < 4; x++) {
paint.setColor([Math.random(), Math.random(), Math.random(), 1]);
c.drawRect(CanvasKit.LTRBRect(x, y, x+1, y+1), paint);
}
}
return surf.makeImageSnapshot();
}();
const imageShader = image.makeShaderOptions(CanvasKit.TileMode.Clamp,
CanvasKit.TileMode.Clamp,
CanvasKit.FilterMode.Nearest,
CanvasKit.MipmapMode.None);
sharpen.oninput = () => { surface.requestAnimationFrame(drawFrame); };
cubic_B.oninput = () => { surface.requestAnimationFrame(drawFrame); };
cubic_C.oninput = () => { surface.requestAnimationFrame(drawFrame); };
const drawFrame = function(canvas) {
const v = sharpen.valueAsNumber;
const m = 1/Math.max(v, 0.00001);
const B = cubic_B.valueAsNumber;
const C = cubic_C.valueAsNumber;
canvas.save();
// Upscale all drawing by 100x; This is big enough to make the differences in technique
// more obvious.
const scale = 100;
canvas.scale(scale, scale);
// Upper left, draw image using an algorithm (written in SkSL) between nearest neighbor and
// linear interpolation with no smoothing.
paint.setShader(effect.makeShaderWithChildren([m, 0], [imageShader], null));
canvas.drawRect(CanvasKit.LTRBRect(0, 0, 4, 4), paint);
// Lower left, draw image using an algorithm (written in SkSL) between nearest neighbor and
// linear interpolation with smoothing enabled.
canvas.save();
canvas.translate(0, 4.1);
paint.setShader(effect.makeShaderWithChildren([m, 1], [imageShader], null));
canvas.drawRect(CanvasKit.LTRBRect(0, 0, 4, 4), paint);
canvas.restore();
// Upper right, draw image with built-in linear interpolation.
canvas.drawImageOptions(image, 4.1, 0, CanvasKit.FilterMode.Linear, CanvasKit.MipmapMode.None, null);
// Lower right, draw image with configurable cubic interpolation.
canvas.drawImageCubic(image, 4.1, 4.1, B, C, null);
canvas.restore();
};
surface.requestAnimationFrame(drawFrame);
});
</script>