WEB Signal 493
Show HN: MergeImage – Merge and stitch images locally in the browser
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Illustration only Photo by Declan Sun on Unsplash
MergeImage is a client-side web tool that lets users combine up to thirty image files locally in the browser and export the result as PNG, JPEG, or WebP without uploading any data.
Because the tool runs entirely in the browser, original files never leave the user's device, providing privacy for sensitive material and eliminating upload/download latency. Engineers can use it for quick compositing tasks without setting up a backend service, but must account for the client-side memory and size limits imposed by the tool.
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The tool processes images entirely in the browser using standard file APIs, keeping originals on the user's device.
It supports up to thirty input files, each up to 20 MB, and offers layout options (horizontal, vertical, grid, smart stitch) with sizing, alignment, background, and export format choices.
Output is automatically scaled down if the resulting canvas would exceed 12,000 pixels on an edge or 80 megapixels, preventing excessive memory use on low-end devices.
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MergeImage introduces a fully local workflow for merging images, removing the need for any server-side processing or account creation. The interface reads files through the browser’s file API, decodes them onto a canvas, and generates the export on the same device. This means network traffic can be inspected to confirm that no original data is transmitted.
The tool enforces explicit limits to protect device resources: a maximum of thirty files, each no larger than 20 MB, and an automatic reduction of the output when the canvas would exceed a 12,000-pixel edge or 80 megapixels. These boundaries are product-defined rather than browser-imposed, making failure modes predictable for developers.
For engineers, adopting MergeImage can replace simple image-stitching microservices or scripts, reducing operational complexity and latency for tasks such as creating contact sheets, before-after comparisons, or screenshot compilations. However, the solution is only suitable when the target audience’s devices can handle the memory demands of the largest allowed inputs and when the required output does not exceed the safety thresholds.
Because the tool provides only basic layout and export options, any need for advanced editing, such as color correction, filtering, or complex masking, must be handled elsewhere. Teams should evaluate whether the local merge capabilities meet their end-to-end workflow or if additional client- or server-side processing will still be required.
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