| .TH IM_MAPLUT 3 "10 May 1991" |
| .SH NAME |
| im_maplut \- map an image through a lookup table |
| .SH SYNOPSIS |
| #include <vips/vips.h> |
| |
| int im_maplut(in, out, lut) |
| .br |
| IMAGE *in, *out, *lut; |
| |
| .SH DESCRIPTION |
| im_maplut() maps an image through another image, acting as a LUT (Look Up |
| Table). The lut may have any type, and the output image will be of that type. |
| |
| The input image must be an unsigned integer types, that is, it must be one of |
| FMTUCHAR, FMTUSHORT or FMTUINT. |
| |
| If the input is FMTUCHAR, then the LUT must have 256 elements, in other words, |
| lut->Xsize * lut->Ysize == 256. |
| |
| If the input is FMTUSHORT or FMTUINT, then the lut may have any number of |
| elements, and input pels whose value is greater than lut->Xsize * lut->Ysize |
| are mapped with the last LUT element. The function counts and prints the |
| number of image elements which overflow in this way. |
| |
| As regards bands, there are three cases: |
| |
| - If LUT has one band, then the input may have any number of bands, and |
| each band will pass through the same LUT. |
| |
| - If LUT has the same number of bands as the input, then each band of the |
| input will be LUTed separately. |
| |
| - If the input has one band, then the LUT may have any number of bands, and |
| the output will have the same number of bands as the LUT. |
| |
| .SH RETURN VALUE |
| All functions returns 0 on success and -1 on error. |
| .SH SEE ALSO |
| im_histgr(3), im_hsp(3), im_heq(3), im_identity(3). |
| .SH COPYRIGHT |
| 1995, National Gallery and Birkbeck College |
| .SH AUTHORS |
| J. Cupitt, 1995 |
| .br |
| N. Dessipris \- 10/05/1991 |
