# ImageMagick - MagickCore, C API: Compute a Message Digest for an Image
Use ImageMagick® to create, edit, compose, and convert bitmap images. Resize an image, crop it, change its shades and colors, add captions, and more.
Author: ImageMagick Studio LLC
Keywords: magickcore, c, api:, compute, a, message, digest, for, an, image, image converter, image resizer, image editor, photo editor, jpg converter, png converter, tiff converter, vector images, online, free, swiss army

SignatureImage

## SignatureImage

SignatureImage() computes a message digest from an image pixel stream with an implementation of the NIST SHA-256 Message Digest algorithm. This signature uniquely identifies the image and is convenient for determining if an image has been modified or whether two images are identical.

The format of the SignatureImage method is:

    MagickBooleanType SignatureImage(Image *image)

A description of each parameter follows:

image
  the image.