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clear canvas #45

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a759719
Update simpleheat.js
treenewbee Apr 7, 2022
9748182
Merge pull request #1 from treenewbee/treenewbee-patch-clear-canvas
treenewbee Apr 7, 2022
1e64cd3
add alpha support
treenewbee Apr 13, 2022
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2 changes: 1 addition & 1 deletion package.json
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
{
"name": "simpleheat",
"version": "0.4.0",
"version": "0.4.1",
"description": "A tiny JavaScript library for drawing heatmaps with Canvas",
"homepage": "https://github.com/mourner/simpleheat",
"keywords": [
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11 changes: 8 additions & 3 deletions simpleheat.js
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@ simpleheat.prototype = {
},

clear: function () {
this._ctx.clearRect(0, 0, this._width, this._height);
this._data = [];
return this;
},
Expand Down Expand Up @@ -95,7 +96,7 @@ simpleheat.prototype = {
return this;
},

draw: function (minOpacity) {
draw: function (minOpacity, alpha) {
if (!this._circle) this.radius(this.defaultRadius);
if (!this._grad) this.gradient(this.defaultGradient);

Expand All @@ -112,20 +113,24 @@ simpleheat.prototype = {

// colorize the heatmap, using opacity value of each pixel to get the right color from our gradient
var colored = ctx.getImageData(0, 0, this._width, this._height);
this._colorize(colored.data, this._grad);
this._colorize(colored.data, this._grad, alpha);
ctx.putImageData(colored, 0, 0);

return this;
},

_colorize: function (pixels, gradient) {
_colorize: function (pixels, gradient, alpha) {
for (var i = 0, len = pixels.length, j; i < len; i += 4) {
j = pixels[i + 3] * 4; // get gradient color from opacity value

if (j) {
pixels[i] = gradient[j];
pixels[i + 1] = gradient[j + 1];
pixels[i + 2] = gradient[j + 2];
if (alpha)
{
pixels[i + 3] = pixels[i + 3] * alpha;
}
}
}
},
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