Load PDF into layer offscreen

Load PDF into layer offscreen

By : Yancyd
Date : January 10 2021, 01:57 PM
Hope that helps Note : you told that You need to load PDF into CALayer. But Here, I have the solution for loading entire pdf pages into images. Once images are in an array, you can view any of them as & when required. Add comment if you have any doubts.
You just have to copy & paste following code. It will almost work for you. I have tested.
code :

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Why does my UIVIew load offscreen?

Why does my UIVIew load offscreen?

By : eadile
Date : March 29 2020, 07:55 AM
it fixes the issue You have to account for the height of the status bar when you add the view to the window:
code :
CGRect statusBarFrame = [[UIApplication sharedApplication] statusBarFrame];
CGSize statusBarSize = statusBarFrame.size;
CGFloat statusBarHeight = statusBarSize.height;

LViewController *aLViewController = [[LViewController alloc] initWithNibName:@"LViewController" bundle:[NSBundle mainBundle]];
self.viewController = aLViewController;
[aLViewController release];  

viewController.view.frame = CGRectMake(0.0f,
                                       window.bounds.size.height - statusBarHeight);

[window addSubview:[viewController view]];
When does a view (or layer) require offscreen rendering?

When does a view (or layer) require offscreen rendering?

By : sfg
Date : March 29 2020, 07:55 AM
it should still fix some issue I don't think there is a rule written down anywhere, but hopefully this will help:
First, let's clear up some definitions. I think offscreen vs onscreen rendering is not the overriding concern most of the time, because offscreen rendering can be as fast as onscreen. The main issue is whether the rendering is done in hardware or software.
Awesomium offscreen webview never load a page

Awesomium offscreen webview never load a page

By : user2112824
Date : March 29 2020, 07:55 AM
will be helpful for those in need I made some research and found instruction here
code :
static void Main(string[] args)
    Task t = new Task(() =>
        WebCore.Initialize(new WebConfig(), true);
        WebView browser = WebCore.CreateWebView(1024, 768, WebViewType.Offscreen);
        browser.DocumentReady += browser_DocumentReady;
        browser.Source = new Uri("https://www.google.ru/");
static void browser_DocumentReady(object sender, UrlEventArgs e)
Javascript load Image into Offscreen Canvas, perform webp conversion

Javascript load Image into Offscreen Canvas, perform webp conversion

By : user2708195
Date : March 29 2020, 07:55 AM
I wish this helpful for you You are facing an XY and even -Z problem here, but each may have an useful answer, so let's dig in.
code :
large.onclick = e => process('https://upload.wikimedia.org/wikipedia/commons/c/cf/Black_hole_-_Messier_87.jpg');
medium.onclick = e => process('https://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Black_hole_-_Messier_87.jpg/1280px-Black_hole_-_Messier_87.jpg');

function process(url) {

async function convertToWebp(url) {
  console.warn("your browser doesn't support webp export, will default to png");

  let img = await loadImage(url);
  if(typeof window.createImageBitmap === 'function') {
    img = await createImageBitmap(img);
  const ctx = get2DContext(img.width, img.height);

  console.time('only sync part');
  ctx.drawImage(img, 0,0);
  console.timeEnd('only sync part');
  return new Promise((res, rej) => {
    ctx.canvas.toBlob( blob => {
      if(!blob) rej(ctx.canvas);
    }, 'image/webp');

// some helpers

function loadImage(url) {
  return new Promise((res, rej) => {
    const img = new Image();
    img.crossOrigin = 'anonymous';
    img.src = url;
    img.onload = e => res(img);
    img.onerror = rej;

function get2DContext(width = 300, height=150) {
  return Object.assign(
    {width, height}

function prepareDownload(blob) {
  const a = document.createElement('a');
  a.href = URL.createObjectURL(blob);
  a.download = 'image.' + blob.type.replace('image/', '');
  a.textContent = 'download';

function supportWebpExport() {
  return get2DContext(1,1).canvas
    .indexOf('image/webp') > -1;
<button id="large">convert large image (7,416 × 4,320 pixels)</button>
<button id="medium">convert medium image (1,280 × 746 pixels)</button>
const img = new Image();
img.onload = e => {
  createImageBitmap(img).then(bmp => {
    // transfer it to your worker
      image: bmp // the key to retrieve it in `event.data`
   [bmp] // transfer it
img.src = url;
const blob = await fetch(url).then(r => r.blob());
const img = await createImageBitmap(blob);
Render layer offscreen

Render layer offscreen

By : Nandan
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , Render your content into an CGBitmapContext, pull a CGImageRef off of that and set that as the contents of the CALayer. Take a look at Creating a Bitmap Graphics Context for example code for most of this.
But if your real problem is that your drawInContext: is too slow, you should first look at breaking that up so that you pre-calculate everything when the data changes and only do drawing in drawInContext:. This is generally the better approach. Don't pre-render the layer itself; pre-calculate everything you need to render the layer quickly. But for very complicated drawing, the CGImageRef approach is useful.
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