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Update the learning/ examples with basic HiDPI-screen support

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This is essentially a simplified version of the code that's used in `PDFPageView`, which will hopefully reduce the number of issues opened specifically about blurry rendering.
However, note that *ideally* users should base their implementations on the `components/` examples rather than using the API directly (the "viewer components" already support HiDPI-screens).
This commit is contained in:
Jonas Jenwald 2021-09-07 14:43:53 +02:00
parent d95f680d66
commit b39cd706a6
4 changed files with 48 additions and 8 deletions
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14
examples/learning/helloworld.html
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@ -36,20 +36,30 @@
pdf.getPage(1).then(function(page) {
var scale = 1.5;
var viewport = page.getViewport({ scale: scale, });
// Support HiDPI-screens.
var outputScale = window.devicePixelRatio || 1;
//
// Prepare canvas using PDF page dimensions
//
var canvas = document.getElementById('the-canvas');
var context = canvas.getContext('2d');
canvas.height = viewport.height;
canvas.width = viewport.width;
canvas.width = Math.floor(viewport.width * outputScale);
canvas.height = Math.floor(viewport.height * outputScale);
canvas.style.width = Math.floor(viewport.width) + "px";
canvas.style.height = Math.floor(viewport.height) + "px";
var transform = outputScale !== 1
? [outputScale, 0, 0, outputScale, 0, 0]
: null;
//
// Render PDF page into canvas context
//
var renderContext = {
canvasContext: context,
transform: transform,
viewport: viewport,
};
page.render(renderContext);