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Reuse temporary canvas in getDataAtPixel()

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This commit is contained in:
mike-000
2021-11-04 13:09:16 +00:00
committed by GitHub
parent fa2f730442
commit 655a49de7b
1 changed files with 20 additions and 9 deletions
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29
src/ol/renderer/canvas/Layer.js
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@@ -76,6 +76,12 @@ class CanvasLayerRenderer extends LayerRenderer {
* @type {boolean}
*/
this.containerReused = false;
/**
* @private
* @type {CanvasRenderingContext2D}
*/
this.pixelContext_ = null;
}
/**
@@ -264,20 +270,25 @@ class CanvasLayerRenderer extends LayerRenderer {
}
}
const x = Math.round(renderPixel[0]);
const y = Math.round(renderPixel[1]);
let pixelContext = this.pixelContext_;
if (!pixelContext) {
const pixelCanvas = document.createElement('canvas');
pixelCanvas.width = 1;
pixelCanvas.height = 1;
pixelContext = pixelCanvas.getContext('2d');
this.pixelContext_ = pixelContext;
}
pixelContext.clearRect(0, 0, 1, 1);
let data;
try {
const x = Math.round(renderPixel[0]);
const y = Math.round(renderPixel[1]);
const newCanvas = document.createElement('canvas');
const newContext = newCanvas.getContext('2d');
newCanvas.width = 1;
newCanvas.height = 1;
newContext.clearRect(0, 0, 1, 1);
newContext.drawImage(context.canvas, x, y, 1, 1, 0, 0, 1, 1);
data = newContext.getImageData(0, 0, 1, 1).data;
pixelContext.drawImage(context.canvas, x, y, 1, 1, 0, 0, 1, 1);
data = pixelContext.getImageData(0, 0, 1, 1).data;
} catch (err) {
if (err.name === 'SecurityError') {
// tainted canvas, we assume there is data at the given pixel (although there might not be)
this.pixelContext_ = null;
return new Uint8Array();
}
return data;