SnapOtter/apps/docs/tools/image/compose.md

description

description
Layer images with position, opacity, and blend modes for compositing.

Image Composition

Layer an overlay image on top of a base image with configurable position, opacity, and blend mode. Useful for compositing logos, graphics, or combining multiple images.

API Endpoint

POST /api/v1/tools/image/compose

Accepts multipart form data with two image files and a JSON settings field.

Parameters

Parameter	Type	Required	Default	Description
x	number	No	0	Horizontal offset of the overlay from the top-left corner in pixels (min 0)
y	number	No	0	Vertical offset of the overlay from the top-left corner in pixels (min 0)
opacity	number	No	100	Overlay opacity percentage (0 to 100)
blendMode	string	No	"over"	Compositing blend mode

Blend Modes

Value	Description
over	Normal overlay (default)
multiply	Darken by multiplying pixel values
screen	Lighten by inverting, multiplying, and inverting again
overlay	Combines multiply and screen based on base brightness
darken	Keep the darker pixel from each layer
lighten	Keep the lighter pixel from each layer
hard-light	Strong contrast overlay
soft-light	Subtle contrast overlay
difference	Absolute difference between layers
exclusion	Similar to difference but lower contrast

File Fields

Field Name	Required	Description
file	Yes	The base/background image
overlay	Yes	The overlay/foreground image

Example Request

curl -X POST http://localhost:1349/api/v1/tools/image/compose \
  -H "Authorization: Bearer si_your-api-key" \
  -F "file=@background.jpg" \
  -F "overlay=@graphic.png" \
  -F 'settings={"x": 100, "y": 50, "opacity": 80, "blendMode": "over"}'

Using multiply blend mode:

curl -X POST http://localhost:1349/api/v1/tools/image/compose \
  -H "Authorization: Bearer si_your-api-key" \
  -F "file=@photo.jpg" \
  -F "overlay=@texture.jpg" \
  -F 'settings={"x": 0, "y": 0, "opacity": 50, "blendMode": "multiply"}'

Example Response

{
  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "downloadUrl": "/api/v1/download/a1b2c3d4-e5f6-7890-abcd-ef1234567890/background.jpg",
  "originalSize": 3200000,
  "processedSize": 3450000
}

Notes

• Both images are validated and decoded (HEIC, RAW, PSD, SVG supported) before compositing.
• The overlay is placed at the exact pixel coordinates specified by x and y. It is not resized to fit.
• If opacity is less than 100, an alpha mask is applied to the overlay before blending.
• The overlay can extend beyond the base image boundaries (it will be clipped).
• EXIF orientation is auto-applied on both images before processing.
• Output dimensions match the base image dimensions.