0xsmw/pixelcop

PixelCop is a macOS tool that analyzes screenshots and draws pixel-perfect measurements directly onto them. If you've ever wanted to know the exact distance between two buttons, the size of a text block, or the margins in an app interface, you feed it a screenshot and it produces an annotated image with all those dimensions mapped out. You run it from the command line, giving it a screenshot file. It decodes the image, uses Apple's built-in text recognition to identify and box any words, and then detects other visual elements like buttons or cards by looking for changes in brightness. From there, it calculates the spacing between those elements and draws colored lines and boxes on top of the image to show the measurements. Along with the marked-up image, it generates a simple report listing all the pixel dimensions and an editable vector file for further tweaking. Designers, developers, and product managers would find this useful when doing layout reviews or trying to match a design spec. For example, if a designer wants to verify that the spacing in the macOS Stocks app matches their Figma file, they can take a screenshot, run it through the tool, and immediately see the exact distances between the sidebar, cards, and text. It is particularly handy for measuring existing apps or interfaces where you don't have access to the underlying code. Everything runs locally on your Mac, so screenshots never leave your machine. The tool is straightforward to install if you are comfortable with the terminal, and it includes options to fine-tune detection sensitivity for images that might be noisy or low contrast. However, since it works purely from pixels, it can't see invisible click targets or underlying code structure, it is meant to provide visual evidence for layout review, not to perfectly reconstruct how an app was built.