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yustier/conicGrad.html

Last active July 29, 2023 13:29
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指定した大きさの色相環の画像を作成する
Raw
conicGrad.html
<!DOCTYPE html>
<html>
<head>
<script>
function draw(canvas, size) {
const ctx = canvas.getContext('2d');
const conicGrad = ctx.createConicGradient(0, size / 2, size / 2);
conicGrad.addColorStop(0, '#f00');
conicGrad.addColorStop(1 / 6, '#f0f');
conicGrad.addColorStop(2 / 6, '#00f');
conicGrad.addColorStop(3 / 6, '#0ff');
conicGrad.addColorStop(4 / 6, '#0f0');
conicGrad.addColorStop(5 / 6, '#ff0');
conicGrad.addColorStop(1, '#f00');
ctx.fillStyle = conicGrad;
ctx.fillRect(0, 0, size, size);
}
window.onload = () => {
const canvas = document.querySelector('#canvas');
canvas.style = 'zoom:' + (100 / window.devicePixelRatio || 100) + '%;';
const size = document.querySelector('#size');
size.addEventListener('change', () => {
canvas.width = size.value;
canvas.height = size.value;
draw(canvas, size.value);
});
const save = document.querySelector('#save');
save.addEventListener('click', () => {
const link = document.createElement('a');
link.href = canvas.toDataURL();
link.download = '';
link.click();
});
draw(canvas, size.value);
};
</script>
</head>
<body>
Size (px):
<input id="size" type="text" value="640">
<input id="save" type="button" value="Save"><br>
<canvas id="canvas" width="640" height="640"></canvas>
</body>
</html>
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