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Scale super large images down so that they can be drawn on the canvas

This commit is contained in:
Maurice Parker 2021-04-07 19:31:46 -05:00
parent b69f936cb1
commit 913e2e0666
1 changed files with 11 additions and 1 deletions
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12
iOS/Resources/main_ios.js
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@ -35,11 +35,21 @@ class ImageViewer {
var canvas = document.createElement("canvas"); var canvas = document.createElement("canvas");
var pixelRatio = window.devicePixelRatio; var pixelRatio = window.devicePixelRatio;
var totalPixels = 0;
do { do {
canvas.width = this.img.naturalWidth * pixelRatio; canvas.width = this.img.naturalWidth * pixelRatio;
canvas.height = this.img.naturalHeight * pixelRatio; canvas.height = this.img.naturalHeight * pixelRatio;
totalPixels = canvas.width * canvas.height;
pixelRatio--; pixelRatio--;
} while (pixelRatio > 0 && canvas.width * canvas.height > 16777216) } while (pixelRatio > 0 && totalPixels > 16777216)
// If the totalPixels is still too big to draw on a canvas, scale it down
if (totalPixels > 16777216) {
var adjustment = 1 - ((totalPixels - 16777216) / totalPixels);
canvas.width = canvas.width * adjustment;
canvas.height = canvas.height * adjustment;
}
canvas.getContext("2d").drawImage(this.img, 0, 0, canvas.width, canvas.height); canvas.getContext("2d").drawImage(this.img, 0, 0, canvas.width, canvas.height);
const rect = this.img.getBoundingClientRect(); const rect = this.img.getBoundingClientRect();