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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →To white out or black out part of a screenshot before printing, draw the screenshot into an HTML canvas, paint fully opaque rectangles over the regions to cover, and print or export that modified canvas. The covered pixels—not a separate overlay—must be what reaches the printer or PDF. This approach works for screenshots you can load into the page; for automated masking of known webpage elements, Playwright offers a different workflow.
Use canvas to cover screenshot regions
A canvas lets JavaScript draw an image and then replace selected areas with solid color. Use white for a white-out or black for a black-out. Because the rectangles are painted into the canvas bitmap, they cover the underlying screenshot when that bitmap is printed.
The HTML Standard describes a canvas as representing its current bitmap and size in static visual media, including print. See the WHATWG HTML Standard. MDN’s canvas element documentation also explains drawing images and the distinction between bitmap dimensions and CSS display dimensions.
Runnable example: load an image and paint rectangles
Save this as an HTML file, place a screenshot named screenshot.png beside it, and open the file in a browser. The example covers two pixel-coordinate regions, shows only the modified canvas in print, and includes buttons to change the cover color and open the print dialog.
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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Cover screenshot areas before printing</title>
<style>
canvas { display: block; max-width: 100%; height: auto; border: 1px solid #999; }
@media print {
@page { size: auto; margin: 12mm; }
body * { visibility: hidden; }
#printArea, #printArea * { visibility: visible; }
#printArea { position: absolute; inset: 0; width: 100%; }
canvas { width: 100%; height: auto; border: 0; }
.controls { display: none; }
}
</style>
</head>
<body>
<div id="printArea">
<canvas id="redacted"></canvas>
</div>
<div class="controls">
<button id="white" type="button">White out</button>
<button id="black" type="button">Black out</button>
<button id="print" type="button">Print</button>
<p id="status" role="status">Loading screenshot…</p>
</div>
<script>
const image = new Image();
image.src = "screenshot.png";
const canvas = document.querySelector("#redacted");
const context = canvas.getContext("2d");
const regions = [
{ x: 80, y: 110, width: 240, height: 42 },
{ x: 80, y: 390, width: 180, height: 36 }
];
let cover = "#fff";
function draw() {
canvas.width = image.naturalWidth;
canvas.height = image.naturalHeight;
context.drawImage(image, 0, 0);
context.fillStyle = cover;
for (const region of regions) {
context.fillRect(region.x, region.y, region.width, region.height);
}
document.querySelector("#status").textContent =
`Ready: ${canvas.width} × ${canvas.height} pixels`;
}
image.addEventListener("load", draw);
image.addEventListener("error", () => {
document.querySelector("#status").textContent =
"Could not load screenshot.png. Check the filename and location.";
});
document.querySelector("#white").addEventListener("click", () => {
cover = "#fff";
draw();
});
document.querySelector("#black").addEventListener("click", () => {
cover = "#000";
draw();
});
document.querySelector("#print").addEventListener("click", () => window.print());
</script>
</body>
</html>The coordinates in regions are measured in the source image’s bitmap pixels, from its top-left corner. Change the rectangles to match the screenshot. The code redraws the original image each time the color changes, then applies the cover; this prevents repeated clicks from layering old fills over the source.
Why set the canvas dimensions from the image?
canvas.width and canvas.height determine its internal bitmap. Setting only CSS width or height changes how the bitmap is displayed and can scale it, which can blur or distort the output. The example uses the image’s natural pixel dimensions for the bitmap and CSS only to fit the preview to the screen or printed page. If you intentionally resize the bitmap, scale both the screenshot and the rectangle coordinates by the same factor.
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Make the cover truly opaque
For privacy, use an opaque fill such as #fff or #000. Do not rely on a visual overlay that sits above the image: if printing or exporting includes the original image instead of the overlay, the sensitive pixels may remain. Export or print the composed canvas itself.
Blur is not a dependable substitute for a solid cover. MDN documents CanvasRenderingContext2D.filter effects such as blur, but marks the property as having limited availability and not Baseline. See MDN’s CanvasRenderingContext2D.filter reference. A blur may also leave recognizable information; use opaque fills where unreadability is the goal.
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Print the modified canvas or export it
Print from the browser
The example calls window.print(). Its @media print rules hide the controls and retain the canvas in the print area. The @page rule sets a margin; you can specify a paper size or orientation there when appropriate. Print behavior also depends on the browser’s print dialog and settings. Inspect Print Preview for scaling, clipping, unwanted blank pages, and whether the canvas is present before printing.
MDN’s printing with CSS guide covers print-specific styles and @page. Browser settings can override or interact with page layout rules, so the preview is the final check.
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Export a PNG file instead
To download the modified bitmap and print it from another application, add this handler after the canvas is drawn:
function downloadRedactedPng() {
canvas.toBlob((blob) => {
if (!blob) {
document.querySelector("#status").textContent = "PNG export failed.";
return;
}
const link = document.createElement("a");
const objectUrl = URL.createObjectURL(blob);
link.href = objectUrl;
link.download = "redacted-screenshot.png";
link.click();
URL.revokeObjectURL(objectUrl);
}, "image/png");
}Call downloadRedactedPng() from a button click after the image has loaded. PNG is a lossless choice for a screenshot. Exporting a modified bitmap makes the filled areas part of the exported image; still open the downloaded file and verify it before sharing or printing.
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Choose between interactive canvas editing and automated masking
| Workflow | Best suited to | How regions are defined | Output considerations |
|---|---|---|---|
| Canvas editing in a page | A person covering selected areas in an existing screenshot | Image pixel coordinates, or a selection UI you build | Print or export the modified canvas bitmap; ensure the coordinates match the original image |
| Playwright locator masking | Automated capture of a page when sensitive content has stable DOM locators | Page elements selected with locators | Masking applies during screenshot capture; PDF output uses print CSS media by default |
Playwright’s screenshot API documents masking selected locators with a solid-color box, and its page.pdf() documentation describes PDF generation and print-media behavior. This is a page-capture technique, not a general editor for arbitrary screenshot regions. Consult the Playwright Page API if your input is a live page and the elements can be selected reliably.
Common problems and fixes
- The cover is misplaced: Rectangle coordinates are relative to the source bitmap, not the displayed CSS size. Use natural pixel dimensions or convert screen coordinates by the display-to-bitmap scale ratio.
- The printed screenshot is cropped or too small: Review print preview and adjust the canvas’s print width,
@pagemargins, paper size, and orientation. A page that is taller or wider than printable space may be scaled by the browser. - The screenshot does not appear: Confirm the image path and filename, wait for its
loadevent before drawing, and inspect the browser console for loading errors. If the image comes from another origin, canvas export can be restricted unless the server permits cross-origin image access; loading a local file avoids that remote-origin issue. - Export fails after drawing a remote image: A cross-origin image without suitable CORS permission can taint the canvas, preventing export. Serve the image from the same origin or configure the image host to allow the requesting origin, then set
image.crossOrigin = "anonymous"before assigningimage.src. - The cover looks transparent: Use an opaque CSS color such as
#fffor#000, not an alpha color likergba(0, 0, 0, 0.4). - The browser prints the unmodified image: Ensure the print stylesheet includes the canvas and not a separate original image element. In the example, only the canvas is placed in
#printArea. - The output looks soft: Keep the canvas bitmap at the source image’s native dimensions; avoid enlarging a smaller bitmap for print. CSS changes its presentation size, not its source detail.
Or skip the browser setup
For a screenshot capture pipeline, ScreenshotNeo can return a screenshot or PDF with one request. Its clean-shot steps accept cookie/consent banners and remove 60+ known consent platforms, newsletter popups, and chat widgets before capture; each step can be turned off. Bot checks/CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and response headers report the page verdict and billing status. Its MCP server provides take_screenshot, get_page_info, and capture_pdf tools for AI agents.
For example, this cURL request captures a page as WebP. See the ScreenshotNeo API documentation for options and response details.
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpThe Free plan includes 1,000 shots per month with no card; paid plans start at $5 for 3,000 shots. ScreenshotNeo captures webpages; use the canvas workflow above when you need to choose and redact arbitrary regions of an existing screenshot. Sign up for ScreenshotNeo’s free plan.
Frequently Asked Questions
Can I use this method to hide information in a screenshot before saving it?
Yes. Export the composed canvas, then open the exported file and confirm the covered regions are solid before sharing it.
Can I print several modified screenshots on one page?
Yes. Place each modified canvas in the print area and adjust the print layout, then check Print Preview for scaling and page breaks.
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