# Batch Image Resizer & Cropper

> Resize or crop up to 30 images at once: exact size, fit, percentage or 1:1, 4:5, 16:9, 9:16. Upload one image or a ZIP with up to 30 images and resize them all the same way: to an exact size (cropped to fill, with a chosen focus point), to fit within a box, by percentage, or cropped to a social-media aspect ratio. Choose the output format and quality and download everything as one ZIP with a per-file report.

Part of usefulweb.site (https://usefulweb.site/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://batchimageresizer.usefulweb.site/ (interactive tool at https://batchimageresizer.usefulweb.site/tool)
- JSON API: POST https://batchimageresizer.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://batchimageresizer.usefulweb.site/api/v1/tool)
- OpenAPI: https://batchimageresizer.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://batchimageresizer.usefulweb.site/mcp - tool `batch_image_resizer`

## Inputs
- images (file, required): Image or ZIP of images - One image (JPG, PNG, WebP, AVIF, GIF, TIFF, HEIC) or a ZIP with up to 30 images, max 50 MB per image and 150 MB in total. Your browser form sends one file, so put several images into a ZIP.
- mode (select): Resize mode
- width (integer): Width - Needed for "Exact size"; for "Fit" give width, height or both.
- height (integer): Height
- percent (number): Percentage - Only for "Scale by percentage".
- aspect (select): Aspect ratio - Only for "Crop to aspect ratio".
- gravity (select): Crop focus - Which part of the image is kept when cropping.
- upscale (boolean): Allow enlarging small images
- format (select): Output format
- quality (integer): Quality - For JPG, WebP and AVIF.
- keepMetadata (boolean): Keep EXIF metadata (camera, date, GPS)

## Method
- Each file in the upload (or ZIP) is identified by its content; files that are not supported images are listed as skipped. The ZIP is read in memory with limits (30 images, 50 MB each, no encrypted or ZIP64 archives).
- Every image is first turned upright using its EXIF orientation. Fit: scaled so it fits inside the box (never enlarged unless allowed). Exact size: scaled to cover the box, then cropped around the chosen focus. Percentage: scaled by the factor. Aspect ratio: the largest centred (or focused) crop with that ratio, then optionally fitted into the box.
- Scaling uses ImageMagick's default high-quality filter (Lanczos when shrinking photos, Mitchell when enlarging). WebP is encoded with cwebp and AVIF with avifenc when installed.
- Metadata is removed unless you keep it; when kept, exiftool copies it back and resets the orientation tag. The ZIP is built with fixed timestamps so the same input gives the same file.

## Limits
- Cropping removes parts of the picture; check the preview before publishing.