The In-Browser Processing Pipeline
When a user selects a 15MB smartphone photo, the browser loads the file as an HTMLImageElement using `URL.createObjectURL()`. A hidden `<canvas>` element draws the image with proportional bilinear scaling, reducing dimensions to the target resolution.
Calling `canvas.toBlob(callback, "image/webp", 0.85)` compresses the raw pixels into a lightweight 120KB WebP file entirely in browser memory in under 80 milliseconds.
Automated Metadata Privacy Stripping
Because drawing an image onto an HTML5 Canvas rasterizes only raw visual pixel data into an RGBA array, all embedded EXIF metadata tags—including home GPS location coordinates and camera serial numbers—are naturally stripped clean from the output.
Step-by-Step Tutorial
Read File as Image Element
Create an Image object and set its src to `URL.createObjectURL(file)`.
Draw Scaled Pixels on Offscreen Canvas
Initialize an offscreen canvas with calculated dimensions and invoke `ctx.drawImage()`.
Export Compressed WebP Blob
Invoke `canvas.toBlob()` with MIME type `image/webp` and quality setting `0.85`.
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Frequently Asked Questions
Does in-browser image processing work inside Web Workers?
Yes! Modern browsers support `OffscreenCanvas`, allowing the entire image decoding, resizing, and WebP compression pipeline to run inside background Web Worker threads without freezing the UI.