| .TH IM_XYZ2disp 3 "2 Decemder 1992" |
| .SH NAME |
| im_LabQ2Lab, im_Lab2LabQ, im_LabQ2LabS, im_LabS2LabQ, im_Lab2LabS, im_LabS2Lab \- pack and unpack LABPACK images. |
| .SH SYNOPSIS |
| #include <vips/vips.h> |
| |
| int im_LabQ2Lab(in, out) |
| .br |
| IMAGE *in, *out; |
| |
| int im_Lab2LabQ(in, out) |
| .br |
| IMAGE *in, *out; |
| |
| int im_Lab2LabS(in, out) |
| .br |
| IMAGE *in, *out; |
| |
| int im_LabS2LabQ(in, out) |
| .br |
| IMAGE *in, *out; |
| |
| int im_LabS2Lab(in, out) |
| .br |
| IMAGE *in, *out; |
| |
| int im_LabQ2LabS(in, out) |
| .br |
| IMAGE *in, *out; |
| |
| .SH DESCRIPTION |
| These functions pack and unpack LAB images. |
| |
| LabQ is Lab packed in to 4 unsigned chars, with the Coding field set to |
| LABPACK. It counts as a coded type, since most operations will not give the |
| correct result on an image of this type. This is the MARC image type. Bits |
| are allocated as 10 for L and 11 for each of a and b. The first three bytes |
| contain the 8 most significant bits of Lab respectively, the final byte has |
| 2/3/3 bits (MSB on left) of Lab respectively. |
| |
| im_LabQ2Lab() and im_Lab2LabQ() convert LABPACK images to three band float |
| images, scaled to look sensible to humans. This is the most convenient LAB |
| format for development work, but is rather slow. |
| |
| im_LabQ2LabS() and im_LabS2LabQ() convert LABPACK to and from three band |
| signed short images. L is shifted and masked to be in the range [0,32767], a |
| and b are shifted and masked to lie in [-32768,32767]. This is the best |
| computational LAB format, combining precision and speed. Programs such as |
| conv(1X) and similarity(1X), which can operate directly on LABPACK images, |
| unpack to LabS for computation. |
| |
| .SH RETURN VALUE |
| The functions return 0 on success and -1 on error. |
| .SH SEE ALSO |
| im_col_XYZ2rgb(3), im_dE_fromdisp(3), im_XYZ2disp(3). |
| .SH COPYRIGHT |
| National Gallery, 1990 - 1993 |
| .SH AUTHOR |
| J. Cupitt \- 21/7/93 |
