Image Compare
Upload two images to compute a pixel-level difference map and a numerical similarity percentage. The output is a diff image highlighting changed regions in red.
API Endpoint
POST /api/v1/tools/compare
Accepts multipart form data with two image files. No settings field is needed.
Parameters
This tool has no configurable parameters. Upload exactly two image files.
| Field | Type | Required | Description |
|---|---|---|---|
| file (first) | file | Yes | The first image |
| file (second) | file | Yes | The second image |
Example Request
bash
curl -X POST http://localhost:1349/api/v1/tools/compare \
-H "Authorization: Bearer si_your-api-key" \
-F "[email protected]" \
-F "[email protected]"Example Response
json
{
"jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
"similarity": 94.52,
"dimensions": { "width": 1920, "height": 1080 },
"downloadUrl": "/api/v1/download/a1b2c3d4-e5f6-7890-abcd-ef1234567890/diff.png",
"originalSize": 4900000,
"processedSize": 280000
}Response Fields
| Field | Type | Description |
|---|---|---|
| jobId | string | Job identifier for downloading the diff image |
| similarity | number | Percentage similarity between the two images (0 to 100) |
| dimensions | object | Width and height used for comparison |
| downloadUrl | string | URL to download the generated diff image |
| originalSize | number | Combined size of both input images in bytes |
| processedSize | number | Size of the diff output image in bytes |
Notes
- Both images are resized to the same dimensions (the maximum of each axis) before comparison.
- The diff image highlights differences in red with opacity proportional to the magnitude of change. Identical or near-identical pixels (difference < 10) are shown as semi-transparent versions of the original.
- Similarity is calculated as the inverse of the average pixel difference across all pixels, expressed as a percentage.
- A similarity of 100% means the images are pixel-identical (at the comparison resolution).
- The diff output is always PNG format regardless of input formats.
- Both images are validated and decoded (HEIC, RAW, PSD, SVG supported) before comparison.
- EXIF orientation is auto-applied on both images before processing.