--- name: "im_blend" section: "3" platform: "linux" package: "libvips-dev" version: "7.20.7-1+b3" release: "Debian 6.0 (Squeeze)" platforms: ["linux"] url: "https://new.carta.tech/im_ifthenelse" --- # im\_blend(3) use an unsigned char image to join two images together Part of [im\_ifthenelse(3)](/im_ifthenelse/3.md). ## NAME im\_ifthenelse - use an unsigned char image to join two images together ## SYNOPSIS **#include \** **int im\_ifthenelse(c, a, b, out)**\ **IMAGE \*c, \*a, \*b, \*out;** **int im\_blend(c, a, b, out)**\ **IMAGE \*c, \*a, \*b, \*out;** ## DESCRIPTION **im\_ifthenelse** builds an output image which uses some pels from a and some from b: if the conditional image c is non-zero at that point, the pel comes from a; if it is zero, the pel comes from b. The conditional image c can have either 1 band, in which case entire pels come either from a or b, or n bands, where n is the number of bands in both a and b, in which case individual band elements are chosen from a and b. Images a and b must match in size, type and number of bands. **[im\_blend(3)](/im_blend/3.md)** works just as [im\_ifthenelse(3)](/im_ifthenelse/3.md), except that instead of selecting between a and b, values in the condition image are used to softly blend between the two. 255 means a only, 0 means b only, 128 means 50:50. ## RETURN VALUE 0 on success and -1 on error. ## SEE ALSO [im\_equal(3)](/im_equal/3.md), im\_and(3). ## COPYRIGHT National Gallery ## AUTHOR J. Cupitt