From 22f703cab05b7cd368f4de9e03991b7664dc5022 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Mon, 1 Sep 2014 13:56:46 +0200 Subject: Initial import of argyll version 1.5.1-8 --- tiff/man/TIFFcolor.3tiff | 268 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 268 insertions(+) create mode 100644 tiff/man/TIFFcolor.3tiff (limited to 'tiff/man/TIFFcolor.3tiff') diff --git a/tiff/man/TIFFcolor.3tiff b/tiff/man/TIFFcolor.3tiff new file mode 100644 index 0000000..a3faf79 --- /dev/null +++ b/tiff/man/TIFFcolor.3tiff @@ -0,0 +1,268 @@ +.\" $Id: TIFFcolor.3tiff,v 1.3 2006/03/23 14:54:02 dron Exp $ +.\" +.\" Copyright (c) 2003, Andrey Kiselev +.\" +.\" Permission to use, copy, modify, distribute, and sell this software and +.\" its documentation for any purpose is hereby granted without fee, provided +.\" that (i) the above copyright notices and this permission notice appear in +.\" all copies of the software and related documentation, and (ii) the names of +.\" Sam Leffler and Silicon Graphics may not be used in any advertising or +.\" publicity relating to the software without the specific, prior written +.\" permission of Sam Leffler and Silicon Graphics. +.\" +.\" THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, +.\" EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY +.\" WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. +.\" +.\" IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR +.\" ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, +.\" OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, +.\" WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF +.\" LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE +.\" OF THIS SOFTWARE. +.\" +.if n .po 0 +.TH COLOR 3TIFF "December 21, 2003" "libtiff" +.SH NAME +TIFFYCbCrToRGBInit, TIFFYCbCrtoRGB, TIFFCIELabToRGBInit, TIFFCIELabToXYZ, +TIFFXYZToRGB \- color conversion routines. +.SH SYNOPSIS +.B "#include " +.sp +.BI "int TIFFYCbCrToRGBInit(TIFFYCbCrToRGB *" ycbcr ", float *" luma ", float *"refBlackWhite" );" +.br +.BI "void TIFFYCbCrtoRGB(TIFFYCbCrToRGB *" ycbcr ", uint32 " Y ", int32 " Cb ", int32 " Cr ", uint32 *" R ", uint32 *" G ", uint32 *" B " );" +.sp +.BI "int TIFFCIELabToRGBInit(TIFFCIELabToRGB *" cielab ", TIFFDisplay *" display ", float *" refWhite ");" +.br +.BI "void TIFFCIELabToXYZ(TIFFCIELabToRGB *" cielab ", uint32 " L ", int32 " a ", int32 " b ", float *" X ", float *" Y ", float *" Z ");" +.br +.BI "void TIFFXYZToRGB(TIFFCIELabToRGB *" cielab ", float " X ", float " Y ", float " Z" , uint32 *" R ", uint32 *" G ", uint32 *" B ");" +.SH DESCRIPTION +TIFF supports several color spaces for images stored in that format. There is +usually a problem of application to handle the data properly and convert +between different colorspaces for displaying and printing purposes. To +simplify this task libtiff implements several color conversion routines +itself. In particular, these routines used in +.B TIFFRGBAImage(3TIFF) +interface. +.PP +.B TIFFYCbCrToRGBInit() +used to initialize +.I YCbCr +to +.I RGB +conversion state. Allocating and freeing of the +.I ycbcr +structure belongs to programmer. +.I TIFFYCbCrToRGB +defined in +.B tiffio.h +as +.PP +.RS +.nf +typedef struct { /* YCbCr->RGB support */ + TIFFRGBValue* clamptab; /* range clamping table */ + int* Cr_r_tab; + int* Cb_b_tab; + int32* Cr_g_tab; + int32* Cb_g_tab; + int32* Y_tab; +} TIFFYCbCrToRGB; +.fi +.RE +.PP +.I luma +is a float array of three values representing proportions of the red, green +and blue in luminance, Y (see section 21 of the TIFF 6.0 specification, where +the YCbCr images discussed). +.I TIFFTAG_YCBCRCOEFFICIENTS +holds that values in TIFF file. +.I refBlackWhite +is a float array of 6 values which specifies a pair of headroom and footroom +image data values (codes) for each image component (see section 20 of the +TIFF 6.0 specification where the colorinmetry fields discussed). +.I TIFFTAG_REFERENCEBLACKWHITE +is responsible for storing these values in TIFF file. Following code snippet +should helps to understand the the technique: +.PP +.RS +.nf +float *luma, *refBlackWhite; +uint16 hs, vs; + +/* Initialize structures */ +ycbcr = (TIFFYCbCrToRGB*) + _TIFFmalloc(TIFFroundup(sizeof(TIFFYCbCrToRGB), sizeof(long)) + + 4*256*sizeof(TIFFRGBValue) + + 2*256*sizeof(int) + + 3*256*sizeof(int32)); +if (ycbcr == NULL) { + TIFFError("YCbCr->RGB", + "No space for YCbCr->RGB conversion state"); + exit(0); +} + +TIFFGetFieldDefaulted(tif, TIFFTAG_YCBCRCOEFFICIENTS, &luma); +TIFFGetFieldDefaulted(tif, TIFFTAG_REFERENCEBLACKWHITE, &refBlackWhite); +if (TIFFYCbCrToRGBInit(ycbcr, luma, refBlackWhite) < 0) + exit(0); + +/* Start conversion */ +uint32 r, g, b; +uint32 Y; +int32 Cb, Cr; + +for each pixel in image + TIFFYCbCrtoRGB(img->ycbcr, Y, Cb, Cr, &r, &g, &b); + +/* Free state structure */ +_TIFFfree(ycbcr); +.fi +.RE +.PP + +.PP +.B TIFFCIELabToRGBInit() +initializes the +.I CIE L*a*b* 1976 +to +.I RGB +conversion state. +.B TIFFCIELabToRGB +defined as +.PP +.RS +.nf +#define CIELABTORGB_TABLE_RANGE 1500 + +typedef struct { /* CIE Lab 1976->RGB support */ + int range; /* Size of conversion table */ + float rstep, gstep, bstep; + float X0, Y0, Z0; /* Reference white point */ + TIFFDisplay display; + float Yr2r[CIELABTORGB_TABLE_RANGE + 1]; /* Conversion of Yr to r */ + float Yg2g[CIELABTORGB_TABLE_RANGE + 1]; /* Conversion of Yg to g */ + float Yb2b[CIELABTORGB_TABLE_RANGE + 1]; /* Conversion of Yb to b */ +} TIFFCIELabToRGB; +.fi +.RE +.PP +.I display +is a display device description, declared as +.PP +.RS +.nf +typedef struct { + float d_mat[3][3]; /* XYZ -> luminance matrix */ + float d_YCR; /* Light o/p for reference white */ + float d_YCG; + float d_YCB; + uint32 d_Vrwr; /* Pixel values for ref. white */ + uint32 d_Vrwg; + uint32 d_Vrwb; + float d_Y0R; /* Residual light for black pixel */ + float d_Y0G; + float d_Y0B; + float d_gammaR; /* Gamma values for the three guns */ + float d_gammaG; + float d_gammaB; +} TIFFDisplay; +.fi +.RE +.PP +For example, the one can use sRGB device, which has the following parameters: +.PP +.RS +.nf +TIFFDisplay display_sRGB = { + { /* XYZ -> luminance matrix */ + { 3.2410F, -1.5374F, -0.4986F }, + { -0.9692F, 1.8760F, 0.0416F }, + { 0.0556F, -0.2040F, 1.0570F } + }, + 100.0F, 100.0F, 100.0F, /* Light o/p for reference white */ + 255, 255, 255, /* Pixel values for ref. white */ + 1.0F, 1.0F, 1.0F, /* Residual light o/p for black pixel */ + 2.4F, 2.4F, 2.4F, /* Gamma values for the three guns */ +}; +.fi +.RE +.PP +.I refWhite +is a color temperature of the reference white. The +.I TIFFTAG_WHITEPOINT +contains the chromaticity of the white point of the image from where the +reference white can be calculated using following formulae: +.PP +.RS +refWhite_Y = 100.0 +.br +refWhite_X = whitePoint_x / whitePoint_y * refWhite_Y +.br +refWhite_Z = (1.0 - whitePoint_x - whitePoint_y) / whitePoint_y * refWhite_X +.br +.RE +.PP +The conversion itself performed in two steps: at the first one we will convert +.I CIE L*a*b* 1976 +to +.I CIE XYZ +using +.B TIFFCIELabToXYZ() +routine, and at the second step we will convert +.I CIE XYZ +to +.I RGB +using +.B TIFFXYZToRGB(). +Look at the code sample below: +.PP +.RS +.nf +float *whitePoint; +float refWhite[3]; + +/* Initialize structures */ +img->cielab = (TIFFCIELabToRGB *) + _TIFFmalloc(sizeof(TIFFCIELabToRGB)); +if (!cielab) { + TIFFError("CIE L*a*b*->RGB", + "No space for CIE L*a*b*->RGB conversion state."); + exit(0); +} + +TIFFGetFieldDefaulted(tif, TIFFTAG_WHITEPOINT, &whitePoint); +refWhite[1] = 100.0F; +refWhite[0] = whitePoint[0] / whitePoint[1] * refWhite[1]; +refWhite[2] = (1.0F - whitePoint[0] - whitePoint[1]) + / whitePoint[1] * refWhite[1]; +if (TIFFCIELabToRGBInit(cielab, &display_sRGB, refWhite) < 0) { + TIFFError("CIE L*a*b*->RGB", + "Failed to initialize CIE L*a*b*->RGB conversion state."); + _TIFFfree(cielab); + exit(0); +} + +/* Now we can start to convert */ +uint32 r, g, b; +uint32 L; +int32 a, b; +float X, Y, Z; + +for each pixel in image + TIFFCIELabToXYZ(cielab, L, a, b, &X, &Y, &Z); + TIFFXYZToRGB(cielab, X, Y, Z, &r, &g, &b); + +/* Don't forget to free the state structure */ +_TIFFfree(cielab); +.fi +.RE +.PP +.SH "SEE ALSO" +.BR TIFFRGBAImage (3TIFF) +.BR libtiff (3TIFF), +.PP +Libtiff library home page: +.BR http://www.remotesensing.org/libtiff/ -- cgit v1.2.3