grd2cpt.c

/*--------------------------------------------------------------------
 *
 *	Copyright (c) 1991-2025 by the GMT Team (https://www.generic-mapping-tools.org/team.html)
 *	See LICENSE.TXT file for copying and redistribution conditions.
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU Lesser General Public License as published by
 *	the Free Software Foundation; version 3 or any later version.
 *
 *	This program is distributed in the hope that it will be useful,
 *	but WITHOUT ANY WARRANTY; without even the implied warranty of
 *	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *	GNU Lesser General Public License for more details.
 *
 *	Contact info: www.generic-mapping-tools.org
 *--------------------------------------------------------------------*/
/*
 * Brief synopsis: grd2cpt reads a 2d binary gridded grdfile and creates a continuous-color-
 * palette CPT, with a non-linear histogram-equalized mapping between
 * hue and data value.  (The linear mapping can be made with grd2cpt.)
 *
 * Creates a cumulative distribution function f(z) describing the data
 * in the grdfile.  f(z) is sampled at z values supplied by the user
 * [with -S option] or guessed from the sample mean and standard deviation.
 * f(z) is then found by looping over the grd array for each z and counting
 * data values <= z.  Once f(z) is found then a master CPT is resampled
 * based on a normalized f(z).
 *
 * Author:	Walter H. F. Smith
 * Date:	1-JAN-2010
 * Version:	6 API
 *
 * Note on KEYS: ED)=f mean -E takes an optional Dataset as argument via the +f modifier.
 */

#include "gmt_dev.h"
#include "longopt/grd2cpt_inc.h"

#define THIS_MODULE_CLASSIC_NAME	"grd2cpt"
#define THIS_MODULE_MODERN_NAME	"grd2cpt"
#define THIS_MODULE_LIB		"core"
#define THIS_MODULE_PURPOSE	"Make linear or histogram-equalized color palette table from grid"
#define THIS_MODULE_KEYS	"<G{+,>C},ED)=f"
#define THIS_MODULE_NEEDS	""
#define THIS_MODULE_OPTIONS	"->RVhbo"

#define GRD2CPT_N_LEVELS	11	/* The default number of levels if nothing is specified */

struct GRD2CPT_CTRL {
	struct GRD2CPT_In {
		bool active;
	} In;
	struct GRD2CPT_Out {	/* -> */
		bool active;
		char *file;
	} Out;
	struct GRD2CPT_A {	/* -A<transp>[+a] */
		bool active;
		unsigned int mode;
		double value;
	} A;
	struct GRD2CPT_C {	/* -C<cpt> or -C<color1>,<color2>[,<color3>,...] */
		bool active;
		char *file;
	} C;
	struct GRD2CPT_D {	/* -D[i|o] */
		bool active;
		unsigned int mode;
	} D;
	struct GRD2CPT_E {	/* -E<nlevels>[+c][+f<file>] */
		bool active;
		bool cdf;
		char *file;
		unsigned int levels;
	} E;
	struct GRD2CPT_F {	 /* -F[R|c|g|h|r|x][+c[<label>]][+k<keys>] */
		bool active;
		bool cat;
		unsigned int model;
		char *label;
		char *key;
	} F;
	struct GRD2CPT_G {	/* -Glow/high for input CPT truncation */
		bool active;
		double z_low, z_high;
	} G;
	struct GRD2CPT_H {	/* -H */
		bool active;
	} H;
	struct GRD2CPT_I {	/* -I[z][c] */
		bool active;
		unsigned int mode;
	} I;
	struct GRD2CPT_L {	/* -L<min_limit>/<max_limit> */
		bool active;
		bool minimum_given, maximum_given;
		double min, max;
	} L;
	struct GRD2CPT_M {	/* -M */
		bool active;
	} M;
	struct GRD2CPT_N {	/* -N */
		bool active;
	} N;
	struct GRD2CPT_Q {	/* -Q[i|o] */
		bool active;
		unsigned int mode;
	} Q;
	struct GRD2CPT_T {	/* -T<start>/<stop>/<inc> or -T<n_levels> */
		bool active;
		bool interpolate;
		unsigned int mode;	/* 0 or 1 (-Tn) */
		unsigned int n_levels;
		double low, high, inc;
		char *file;
	} T;
	struct GRD2CPT_S {	/* -S<kind> */
		bool active;
		int kind; /* -1 symmetric +-zmin, +1 +-zmax, -2 = +-Minx(|zmin|,|zmax|), +2 = +-Max(|zmin|,|zmax|), 0 = min to max [Default] */
	} S;
	struct GRD2CPT_W {	/* -W[w] */
		bool active;
		bool wrap;
	} W;
	struct GRD2CPT_Z {	/* -Z */
		bool active;
	} Z;
};

static void *New_Ctrl (struct GMT_CTRL *GMT) {	/* Allocate and initialize a new control structure */
	struct GRD2CPT_CTRL *C;

	C = gmt_M_memory (GMT, NULL, 1, struct GRD2CPT_CTRL);

	/* Initialize values whose defaults are not 0/false/NULL */
	C->G.z_low = C->G.z_high = GMT->session.d_NaN;	/* No truncation */
	return (C);
}

static void Free_Ctrl (struct GMT_CTRL *GMT, struct GRD2CPT_CTRL *C) {	/* Deallocate control structure */
	if (!C) return;
	gmt_M_str_free (C->Out.file);
	gmt_M_str_free (C->C.file);
	gmt_M_str_free (C->E.file);
	gmt_M_str_free (C->F.label);
	gmt_M_str_free (C->T.file);
	gmt_M_free (GMT, C);
}

static int usage (struct GMTAPI_CTRL *API, int level) {
	const char *name = gmt_show_name_and_purpose (API, THIS_MODULE_LIB, THIS_MODULE_CLASSIC_NAME, THIS_MODULE_PURPOSE);
	const char *H_OPT = (API->GMT->current.setting.run_mode == GMT_MODERN) ? " [-H]" : "";
	if (level == GMT_MODULE_PURPOSE) return (GMT_NOERROR);
	GMT_Usage (API, 0, "usage: %s %s [-A<transparency>[+a]] [-C<cpt>] [-D[i|o]] [-E[<nlevels>][+c][+f<file>]] "
		"[-F%s] [-G<zlo>/<zhi>]%s [-I[c][z]] [-L<min_limit>/<max_limit>] [-M] [-N] [-Q[i|o]] "
		"[%s] [-Sh|l|m|u] [-T<start>/<stop>/<inc>|<n>] [%s] [-W[w]] [-Z] [%s] [%s] [%s] [%s]\n",
		name, GMT_INGRID, GMT_COLORMODES_OPT, H_OPT, GMT_Rgeo_OPT, GMT_V_OPT, GMT_bo_OPT, GMT_ho_OPT, GMT_o_OPT, GMT_PAR_OPT);

	if (level == GMT_SYNOPSIS) return (GMT_MODULE_SYNOPSIS);

	GMT_Message (API, GMT_TIME_NONE, "  REQUIRED ARGUMENTS:\n");
	gmt_ingrid_syntax (API, 0, "Name of one or more grid files");
	GMT_Message (API, GMT_TIME_NONE, "\n  OPTIONAL ARGUMENTS:\n");
	GMT_Usage (API, 1, "\n-A<transparency>[+a]");
	GMT_Usage (API, -2, "Set constant transparency for all colors; append +a to also include back-, for-, and nan-colors [0].");
	if (gmt_list_cpt (API->GMT, 'C')) return (GMT_CPT_READ_ERROR);	/* Display list of available color tables */
	GMT_Usage (API, 1, "\n-D[i|o]");
	GMT_Usage (API, -2, "Set back- and foreground color to match the bottom/top limits "
		"in the output CPT [Default (-D or -Do) uses color output table]. Append i "
		"to match the bottom/top values in the input CPT instead.");
	GMT_Usage (API, 1, "\n-E[<nlevels>][+c][+f<file>]");
	GMT_Usage (API, -2, "Set CPT to go from grid zmin to zmax (i.e., a linear scale). "
		"Alternatively, append <nlevels> to sample equidistant color levels from zmin to zmax. "
		"Instead, append +c to use the cumulative density function (cdf) to set color bounds. "
		"Append +f<file> to save the CDF table to a file.");
	gmt_explain_cpt_output (API, 'F');
	GMT_Usage (API, 1, "\n-G<zlo>/<zhi>");
	GMT_Usage (API, -2, "Truncate incoming CPT to be limited to the z-range <zlo>/<zhi>. "
		"To accept one of the incoming limits, set that limit to NaN.");
	GMT_Usage (API, 1, "\n-H Modern mode only: Also write CPT to standard output [Default just saves as current CPT].");
	GMT_Usage (API, 1, "\n-I[c][z]");
	GMT_Usage (API, -2, "Invert sense of CPT in one or two ways:");
	GMT_Usage (API, 3, "c: Invert sense of color table as well as back- and foreground color [Default].");
	GMT_Usage (API, 3, "z: Invert sign of z-values in the color table (takes affect before -G, T are consulted).");
	GMT_Usage (API, 1, "\n-L<min_limit>/<max_limit>");
	GMT_Usage (API, -2, "Limit the range of the data.  Node values outside this range are set to NaN. "
		"To only give min or max limit, set the other to - [Default uses actual min,max of data].");
	GMT_Usage (API, 1, "\n-M Use GMT defaults to set back-, foreground, and NaN colors [Default uses color table].");
	GMT_Usage (API, 1, "\n-N Do not write back-, foreground, and NaN colors [Default will].");
	GMT_Usage (API, 1, "\n-Q[i|o]");
	GMT_Usage (API, -2, "Assign a logarithmic colortable [Default is linear]. Append mode:");
	GMT_Usage (API, 3, "i: z-values are actually log10(z). Assign colors and write z [Default].");
	GMT_Usage (API, 3, "o: z-values are z, but take log10(z), assign colors and write z.");
	GMT_Option (API, "R");
	GMT_Usage (API, 1, "\n-Sh|l|m|u");
	GMT_Usage (API, -2, "Force color tables to be symmetric about 0. Append one modifier:");
	GMT_Usage (API, 3, "l: (low) for values symmetric about zero from -|zmin| to +|zmin|.");
	GMT_Usage (API, 3, "u: (upper) for values symmetric about zero from -|zmax| to +|zmax|.");
	GMT_Usage (API, 3, "m: (min) for values symmetric about zero -+min(|zmin|,|zmax|).");
	GMT_Usage (API, 3, "h: (high) for values symmetric about zero -+max(|zmin|,|zmax|).");
	GMT_Usage (API, 1, "\n-T<start>/<stop>/<inc>|<n>");
	GMT_Usage (API, -2, "CDF sample points should range from <start> to <stop> by <inc>. "
		"Alternatively, use -T<n> to select <n> points from a cumulative normal distribution [%d]. "
		"Here, <start> maps to data min and <stop> maps to data max (but see -L) "
		"[Default uses equidistant steps for a Gaussian CDF].", GRD2CPT_N_LEVELS);
	GMT_Option (API, "V");
	GMT_Usage (API, 1, "\n-W[w]");
	GMT_Usage (API, -2, "Do not interpolate color palette. Alternatively, append w for a wrapped CPT.");
	GMT_Usage (API, 1, "\n-Z Force a continuous color palette [Default is discontinuous, i.e., constant color intervals].");
	GMT_Option (API, "bo,h,o,.");

	return (GMT_MODULE_USAGE);
}

static int parse (struct GMT_CTRL *GMT, struct GRD2CPT_CTRL *Ctrl, struct GMT_OPTION *options) {
	/* This parses the options provided to grdcut and sets parameters in CTRL.
	 * Any GMT common options will override values set previously by other commands.
	 * It also replaces any file names specified as input or output with the data ID
	 * returned when registering these sources/destinations with the API.
	 */

	int n;
	unsigned int n_errors = 0, pos = 0, n_files = 0;
	char txt_a[GMT_LEN512] = {""}, txt_b[GMT_LEN32] = {""}, *c = NULL;
	char *T_arg = NULL, *S_arg = NULL;
	struct GMT_OPTION *opt = NULL;
	struct GMTAPI_CTRL *API = GMT->parent;

	for (opt = options; opt; opt = opt->next) {
		switch (opt->option) {

			case '<':	/* Input files (repeatable - check if they exist) */
				Ctrl->In.active = true;
				n_files++;
				if (GMT_Get_FilePath (API, GMT_IS_GRID, GMT_IN, GMT_FILE_REMOTE, &(opt->arg))) n_errors++;
				break;
			case '>':	/* Got named output file */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->Out.active);
				n_errors += gmt_get_required_file (GMT, opt->arg, opt->option, 0, GMT_IS_DATASET, GMT_OUT, GMT_FILE_LOCAL, &(Ctrl->Out.file));
				break;

			/* Processes program-specific parameters */

			case 'A':	/* Sets transparency [-A<transp>[+a]] */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->A.active);
				if (opt->arg[0] == '+') {	/* Old syntax */
					Ctrl->A.mode = 1;
					Ctrl->A.value = 0.01 * atof (&opt->arg[1]);
				}
				else if ((c = strstr (opt->arg, "+a"))) {
					Ctrl->A.mode = 1;
					c[0] = '\0';
					Ctrl->A.value = 0.01 * atof (opt->arg);
					c[0] = '+';
				}
				else
					Ctrl->A.value = 0.01 * atof (opt->arg);
				break;
			case 'C':	/* Get CPT */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->C.active);
				if (opt->arg[0]) Ctrl->C.file = strdup (opt->arg);
				break;
			case 'D':	/* Set fore/back-ground to match end-colors */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->D.active);
				Ctrl->D.mode = 1;
				if (opt->arg[0] == 'i') Ctrl->D.mode = 2;
				break;
			case 'E':	/* Use n levels */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->E.active);
				if (opt->arg[0]) {	/* Got an argument */
					if (gmt_validate_modifiers (GMT, opt->arg, 'E', "cf", GMT_MSG_ERROR)) n_errors++;
					if ((c = gmt_first_modifier (GMT, opt->arg, "cf")) ) {
						while (gmt_getmodopt (GMT, 'E', c, "cf", &pos, txt_a, &n_errors) && n_errors == 0) {
							switch (txt_a[0]) {
								case 'c': Ctrl->E.cdf = true;	break;	/* Determine Cumulative Density Function */
								case 'f':
									if (txt_a[1])
										Ctrl->E.file = strdup (&txt_a[1]);
									else {
										GMT_Report (API, GMT_MSG_ERROR, "Option -E: No filename given via +f\n");
										n_errors++;
									}
									break;	/* Incremental distance */
								default: break;	/* These are caught in gmt_getmodopt so break is just for Coverity */
							}
						}
						c[0] = '\0';	/* Chop off the modifiers */
					}
					if (sscanf (opt->arg, "%d", &Ctrl->E.levels) != 1) {
						GMT_Report (API, GMT_MSG_ERROR, "Option -E: Cannot decode value given\n");
						n_errors++;
					}
					if (c) c[0] = '+';	/* Restore modifiers */
				}
				break;
			case 'F':	/* Set color model for output */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->F.active);
				if (gmt_validate_modifiers (GMT, opt->arg, 'F', "ck", GMT_MSG_ERROR)) n_errors++;
				if (gmt_get_modifier (opt->arg, 'c', txt_a)) {
					Ctrl->F.cat = true;
					if (txt_a[0]) Ctrl->F.label = strdup (txt_a);
				}
				if (gmt_get_modifier (opt->arg, 'k', txt_a)) {
					Ctrl->F.cat = true;
					if (txt_a[0]) Ctrl->F.key = strdup (txt_a);
				}
				switch (opt->arg[0]) {
					case '\0': case '+': case 'R': Ctrl->F.model = GMT_RGB; break;
					case 'r': Ctrl->F.model = GMT_RGB + GMT_NO_COLORNAMES; break;
					case 'g': Ctrl->F.model = GMT_GRAY; break;
					case 'h': Ctrl->F.model = GMT_HSV; break;
					case 'c': Ctrl->F.model = GMT_CMYK; break;
					case 'x': Ctrl->F.model = GMT_RGB + GMT_HEX_COLOR; break;
					default:
						GMT_Report (API, GMT_MSG_ERROR, "Option -F: Unrecognized directive %c\n", opt->arg[0]);
						n_errors++;
						break;
				}
				break;
			case 'G':	/* truncate incoming CPT */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->G.active);
				n_errors += gmt_get_limits (GMT, 'G', opt->arg, 0, &Ctrl->G.z_low, &Ctrl->G.z_high);
				break;
			case 'H':	/* Modern mode only: write CPT to stdout */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->H.active);
				n_errors += gmt_get_no_argument (GMT, opt->arg, opt->option, 0);
				break;
			case 'I':	/* Invert table */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->I.active);
				if ((Ctrl->I.mode = gmt_parse_inv_cpt (GMT, opt->arg)) == UINT_MAX)
					n_errors++;
				break;
			case 'L':	/* Limit data range */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->L.active);
				if ((n = sscanf (opt->arg, "%[^/]/%s", txt_a, txt_b)) != 2) {
					GMT_Report (API, GMT_MSG_ERROR, "Option -L: Cannot decode two limits\n");
					n_errors++;
				}
				else {	/* Assign limits unless give as "-" which means to skip that limit */
					if (strcmp (txt_a, "-")) Ctrl->L.min = atof (txt_a), Ctrl->L.minimum_given = true;
					if (strcmp (txt_b, "-")) Ctrl->L.max = atof (txt_b), Ctrl->L.maximum_given = true;
				}
				break;
			case 'M':	/* Override fore/back/NaN using GMT defaults */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->M.active);
				n_errors += gmt_get_no_argument (GMT, opt->arg, opt->option, 0);
				break;
			case 'N':	/* Do not write F/B/N colors */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->N.active);
				n_errors += gmt_get_no_argument (GMT, opt->arg, opt->option, 0);
				break;
			case 'Q':	/* Logarithmic data */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->Q.active);
				if (opt->arg[0] == 'o')	/* Input data is z, but take log10(z) before interpolation colors */
					Ctrl->Q.mode = 2;
				else			/* Input is log10(z) */
					Ctrl->Q.mode = 1;
				break;
			case 'T':	/* Sets sample range */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->T.active);
				T_arg = opt->arg;
				break;
			case 'S':	/* Force symmetry */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->S.active);
				S_arg = opt->arg;
				break;
			case 'W':	/* Do not interpolate colors */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->W.active);
				if (opt->arg[0] == 'w') {
					Ctrl->W.wrap = true;
					Ctrl->W.active = false;
				}
				break;
			case 'Z':	/* Continuous colors */
				n_errors += gmt_M_repeated_module_option (API, Ctrl->Z.active);
				n_errors += gmt_get_no_argument (GMT, opt->arg, opt->option, 0);
				break;

			default:	/* Report bad options */
				n_errors += gmt_default_option_error (GMT, opt);
				break;
		}
	}

	if (T_arg) {	/* Must handle old or new syntax */
		if (strchr ("-+_=", T_arg[0]) && T_arg[1] == '\0') {	/* Old -Targs for symmetry given */
			if (gmt_M_compat_check (GMT, 5)) {	/* OK to parse that? */
				GMT_Report (API, GMT_MSG_COMPAT, "Option -T-|+|_|= is deprecated; use -Sl|u|m|h instead.\n");
				Ctrl->S.active = true;
				if (!S_arg) Ctrl->T.active = false;
				switch (T_arg[0]) {
					case '-': Ctrl->S.kind = -1; break; /* Symmetric with |zmin| range */
					case '+': Ctrl->S.kind = +1; break; /* Symmetric with |zmax| range */
					case '_': Ctrl->S.kind = -2; break; /* Symmetric with min(|zmin|,|zmax|) range */
					case '=': Ctrl->S.kind = +2; break; /* Symmetric with max(|zmin|,|zmax|) range */
					default: break;
				}
			}
			else {
				GMT_Report (API, GMT_MSG_ERROR, "Option -T: Cannot decode values %s\n", T_arg);
				n_errors++;
			}
		}
		else {	/* Got correct modern args */
			if (strchr (T_arg, '/')) {	/* Gave low/high/inc */
				if (sscanf (T_arg, "%lf/%lf/%lf", &Ctrl->T.low, &Ctrl->T.high, &Ctrl->T.inc) != 3) {
					GMT_Report (API, GMT_MSG_ERROR, "Option -T: Cannot decode values\n");
					n_errors++;
				}
				Ctrl->T.mode = 0;
			}
			else if (T_arg[0]) {	/* Gave -T<nlevels> */
				Ctrl->T.n_levels = atoi (T_arg);
				Ctrl->T.mode = 1;
			}
		}
	}
	if (S_arg) {	/* Must handle old or new syntax */
		if (strchr ("hlmu", S_arg[0]) && S_arg[1] == '\0') {	/* New -S for symmetry */
			switch (S_arg[0]) {
				case 'l': Ctrl->S.kind = -1; break; /* Symmetric with |zmin| range */
				case 'u': Ctrl->S.kind = +1; break; /* Symmetric with |zmax| range */
				case 'm': Ctrl->S.kind = -2; break; /* Symmetric with min(|zmin|,|zmax|) range */
				case 'h': Ctrl->S.kind = +2; break; /* Symmetric with max(|zmin|,|zmax|) range */
				default: break;
			}
		}
		else if (gmt_M_compat_check (GMT, 5)) {	/* Old-style -S range */
			GMT_Report (API, GMT_MSG_COMPAT, "Option -S<start>/<stop>/<inc> or -S<n> is deprecated; use -T instead.\n");
			if (strchr (S_arg, '/')) {	/* Gave low/high/inc */
				if (sscanf (S_arg, "%lf/%lf/%lf", &Ctrl->T.low, &Ctrl->T.high, &Ctrl->T.inc) != 3) {
					GMT_Report (API, GMT_MSG_ERROR, "Option -T: Cannot decode values %s\n", S_arg);
					n_errors++;
				}
				Ctrl->T.mode = 0;
			}
			else if (S_arg[0]) {	/* Gave -S<nlevels> */
				Ctrl->T.n_levels = atoi (S_arg);
				Ctrl->T.mode = 1;
			}
			if (!T_arg) Ctrl->S.active = false;
			Ctrl->T.active = true;
		}
		else {
			GMT_Report (API, GMT_MSG_ERROR, "Option -S: Cannot decode values %s\n", S_arg);
			n_errors++;
		}
	}

	if (Ctrl->H.active && GMT->current.setting.run_mode == GMT_CLASSIC) {
		GMT_Report (API, GMT_MSG_WARNING, "Option -H: Only available in modern mode - ignored in classic mode\n");
		Ctrl->H.active = false;
	}
	n_errors += gmt_M_check_condition (GMT, Ctrl->C.active && Ctrl->C.file == NULL,
			"Options -C: No CPT argument given\n");
	n_errors += gmt_M_check_condition (GMT, n_files < 1, "No grid name(s) specified.\n");
	n_errors += gmt_M_check_condition (GMT, Ctrl->W.active && Ctrl->Z.active,
					"Options -W and -Z cannot be used simultaneously\n");
	n_errors += gmt_M_check_condition (GMT, Ctrl->F.cat && Ctrl->Z.active,
	                                "Options -F+c and -Z cannot be used simultaneously\n");
	n_errors += gmt_M_check_condition (GMT, Ctrl->L.active && Ctrl->L.minimum_given && Ctrl->L.maximum_given && Ctrl->L.min >= Ctrl->L.max,
					"Option -L: min_limit must be less than max_limit.\n");
	n_errors += gmt_M_check_condition (GMT, Ctrl->T.active && Ctrl->T.mode == 0 && (Ctrl->T.high <= Ctrl->T.low || Ctrl->T.inc <= 0.0),
					"Option -T: Bad arguments\n");
	n_errors += gmt_M_check_condition (GMT, Ctrl->T.active && Ctrl->T.mode == 1  && Ctrl->T.n_levels == 0,
					"Option -T: Bad arguments\n");
	n_errors += gmt_M_check_condition (GMT, Ctrl->T.active && (Ctrl->S.active || Ctrl->E.active),
					"Option -T: Cannot be combined with -E nor -S option.\n");
	n_errors += gmt_M_check_condition (GMT, Ctrl->E.file && !Ctrl->E.cdf, "Option -E modifier +f is only valid if +c is used\n");
	n_errors += gmt_M_check_condition (GMT, Ctrl->A.active && (Ctrl->A.value < 0.0 || Ctrl->A.value > 1.0),
					"Option -A: Transparency must be n 0-100 range [0 or opaque]\n");

	return (n_errors ? GMT_PARSE_ERROR : GMT_NOERROR);
}

GMT_LOCAL int grd2cpt_free_the_grids (struct GMTAPI_CTRL *API, struct GMT_GRID **G, char **grdfile, uint64_t n) {
	/* Free what we are pointing to */
	uint64_t k;
	for (k = 0; k < n; k++) {
		gmt_M_str_free (grdfile[k]);
		if (GMT_Destroy_Data (API, &G[k]) != GMT_NOERROR)
			return (API->error);
	}
	return (GMT_NOERROR);
}

#define bailout(code) {gmt_M_free_options (mode); return (code);}
#define Return(code) {Free_Ctrl (GMT, Ctrl); gmt_end_module (GMT, GMT_cpy); bailout (code);}

EXTERN_MSC int gmtlib_compare_observation (const void *a, const void *b);

EXTERN_MSC int GMT_grd2cpt (void *V_API, int mode, void *args) {
	uint64_t ij, k, ngrd = 0, nxyg, nxy = 0, nfound, ngood;
	openmp_int row, col;
	unsigned int j, cpt_flags = 0;
	int signed_levels, error = 0;
	size_t n_alloc = GMT_TINY_CHUNK;
	bool write = false, interpolate = true;

	char format[GMT_BUFSIZ] = {""}, **grdfile = NULL;

	double *z = NULL, wesn[4], mean, sd, wsum = 0.0, scale;

	struct CDF_CPT {
		double	z;	/* Data value  */
		double	f;	/* Cumulative distribution function f(z)  */
	} *cdf_cpt = NULL;

	struct GMT_OPTION *opt = NULL;
	struct GMT_PALETTE *Pin = NULL, *Pout = NULL;
	struct GMT_GRID **G, *W = NULL;
	struct GMT_OBSERVATION *pair = NULL;
	struct GRD2CPT_CTRL *Ctrl = NULL;
	struct GMT_CTRL *GMT = NULL, *GMT_cpy = NULL;
	struct GMT_OPTION *options = NULL;
	struct GMTAPI_CTRL *API = gmt_get_api_ptr (V_API);	/* Cast from void to GMTAPI_CTRL pointer */

	/*----------------------- Standard module initialization and parsing ----------------------*/

	if (API == NULL) return (GMT_NOT_A_SESSION);
	if (mode == GMT_MODULE_PURPOSE) return (usage (API, GMT_MODULE_PURPOSE));	/* Return the purpose of program */
	options = GMT_Create_Options (API, mode, args);	if (API->error) return (API->error);	/* Set or get option list */

	if ((error = gmt_report_usage (API, options, 0, usage)) != GMT_NOERROR) bailout (error);	/* Give usage if requested */

	/* Parse the command-line arguments */

	if ((GMT = gmt_init_module (API, THIS_MODULE_LIB, THIS_MODULE_CLASSIC_NAME, THIS_MODULE_KEYS, THIS_MODULE_NEEDS, module_kw, &options, &GMT_cpy)) == NULL) bailout (API->error); /* Save current state */
	if (GMT_Parse_Common (API, THIS_MODULE_OPTIONS, options)) Return (API->error);
	Ctrl = New_Ctrl (GMT);	/* Allocate and initialize a new control structure */
	if ((error = parse (GMT, Ctrl, options)) != 0) Return (error);

	/*---------------------------- This is the grd2cpt main code ----------------------------*/

	if (!Ctrl->C.active) {	/* No table specified; set GMT->current.setting.cpt table */
		Ctrl->C.active = true;
		Ctrl->C.file = strdup (GMT->current.setting.cpt);
	}

	if (!Ctrl->E.active) Ctrl->E.levels = (Ctrl->T.n_levels > 0) ? Ctrl->T.n_levels : GRD2CPT_N_LEVELS;	/* Default number of levels */
	if (Ctrl->E.cdf && Ctrl->E.levels == 0) Ctrl->E.levels = GRD2CPT_N_LEVELS;
	if (Ctrl->M.active) cpt_flags |= GMT_CPT_NO_BNF;		/* bit 0 controls if BFN is determined by parameters */
	if (Ctrl->D.mode == 2) cpt_flags |= GMT_CPT_EXTEND_BNF;		/* bit 1 controls if BF will be set to equal bottom/top rgb value */
	if (Ctrl->Z.active) cpt_flags |= GMT_CPT_CONTINUOUS;	/* Controls if final CPT should be continuous in case input is a list of colors */

	if ((Pin = GMT_Read_Data (API, GMT_IS_PALETTE, GMT_IS_FILE, GMT_IS_NONE, cpt_flags, NULL, Ctrl->C.file, NULL)) == NULL) {
		Return (API->error);
	}
	if ((API->error = gmt_validate_cpt_parameters (GMT, Pin, Ctrl->C.file, &interpolate, &(Ctrl->Z.active))))
			Return (API->error)

	if (Ctrl->I.mode & GMT_CPT_Z_REVERSE)	/* Must reverse the z-values before anything else */
		gmt_scale_cpt (GMT, Pin, -1.0);

	if (Ctrl->G.active) {	/* Attempt truncation */
		struct GMT_PALETTE *Ptrunc = gmt_truncate_cpt (GMT, Pin, Ctrl->G.z_low, Ctrl->G.z_high);	/* Possibly truncate the CPT */
		if (Ptrunc == NULL)
			Return (EXIT_FAILURE);
		Pin = Ptrunc;
	}
	if (Ctrl->W.wrap) Pin->is_wrapping = true;	/* A cyclic CPT has been requested */

	write = (GMT->current.setting.run_mode == GMT_CLASSIC || Ctrl->H.active);	/* Only output to stdout in classic mode and with -H in modern mode */

	GMT_Report (API, GMT_MSG_INFORMATION, "Processing input grid(s)\n");

	gmt_M_memset (wesn, 4, double);
	if (GMT->common.R.active[RSET]) gmt_M_memcpy (wesn, GMT->common.R.wesn, 4, double);	/* Subset */

	G = gmt_M_memory (GMT, NULL, n_alloc, struct GMT_GRID *);	/* Potentially an array of grids */
	grdfile = gmt_M_memory (GMT, NULL, n_alloc, char *);	/* Potentially an array of gridfile names */

	for (opt = options, k = 0; opt; opt = opt->next) {
		if (opt->option != '<') continue;	/* We are only processing input files here */

		if ((G[k] = GMT_Read_Data (API, GMT_IS_GRID, GMT_IS_FILE, GMT_IS_SURFACE, GMT_CONTAINER_AND_DATA, wesn, opt->arg, NULL)) == NULL) {
			error = grd2cpt_free_the_grids (API, G, grdfile, k);
			gmt_M_free (GMT, G);
			gmt_M_free (GMT, grdfile);
			Return ((error) ? error : API->error);
		}
		grdfile[k] = strdup (opt->arg);
		if (k && !(G[k]->header->n_columns == G[k-1]->header->n_columns && G[k]->header->n_rows == G[k-1]->header->n_rows)) {
			GMT_Report (API, GMT_MSG_ERROR, "Grids do not have the same domain!\n");
			error = grd2cpt_free_the_grids (API, G, grdfile, k);
			gmt_M_free (GMT, G);
			gmt_M_free (GMT, grdfile);
			Return ((error) ? error : API->error);
		}

		k++;
		if (k == n_alloc) {
			size_t old_n_alloc = n_alloc;
			n_alloc += GMT_TINY_CHUNK;
			G = gmt_M_memory (GMT, G, n_alloc, struct GMT_GRID *);
			gmt_M_memset (&(G[old_n_alloc]), n_alloc - old_n_alloc, struct GMT_GRID *);	/* Set to NULL */
			grdfile = gmt_M_memory (GMT, grdfile, n_alloc, char *);
			gmt_M_memset (&(grdfile[old_n_alloc]), n_alloc - old_n_alloc, char *);	/* Set to NULL */
		}
	}

	ngrd = k;
	if (ngrd < n_alloc) {
		G = gmt_M_memory (GMT, G, ngrd, struct GMT_GRID *);
		grdfile = gmt_M_memory (GMT, grdfile, ngrd, char *);
	}

	nxyg = G[0]->header->nm * ngrd;

	if (Ctrl->E.cdf) {
		pair = gmt_M_memory (GMT, NULL, nxyg, struct GMT_OBSERVATION);
		W = gmt_duplicate_grid (GMT, G[0], GMT_DUPLICATE_ALLOC);
		/* Determine the area weights */
		gmt_get_cellarea (GMT, W);
	}

	/* Loop over the files and find NaNs.  If set limits, may create more NaNs  */
	/* We use the G[0]->header to keep limits representing all the grids */

	nfound = 0;
	mean = sd = 0.0;
	if (Ctrl->L.active) {	/* Loop over the grdfiles, and set anything outside the limiting values to NaN.  */
		G[0]->header->z_min = (Ctrl->L.minimum_given) ? Ctrl->L.min : G[0]->header->z_max;
		G[0]->header->z_max = (Ctrl->L.maximum_given) ? Ctrl->L.max : G[0]->header->z_min;
		for (k = 0; k < ngrd; k++) {	/* For each grid */
			gmt_M_grd_loop (GMT, G[k], row, col, ij) {
				if (gmt_M_is_fnan (G[k]->data[ij]))
					nfound++;
				else {
					if (Ctrl->L.minimum_given && G[k]->data[ij] < Ctrl->L.min) {
						nfound++;
						G[k]->data[ij] = GMT->session.f_NaN;
					}
					else if (Ctrl->L.maximum_given && G[k]->data[ij] > Ctrl->L.max) {
						nfound++;
						G[k]->data[ij] = GMT->session.f_NaN;
					}
					else if (Ctrl->E.cdf) {
						pair[nxy].value    = G[k]->data[ij];
						pair[nxy++].weight = W->data[ij];
						wsum += W->data[ij];
					}
					else {
						mean += G[k]->data[ij];
						sd += G[k]->data[ij] * G[k]->data[ij];
						if (!Ctrl->L.minimum_given && G[k]->data[ij] < Ctrl->L.min) Ctrl->L.min = G[k]->data[ij];
						if (!Ctrl->L.maximum_given && G[k]->data[ij] > Ctrl->L.max) Ctrl->L.max = G[k]->data[ij];
					}
				}
			}
		}
		if (!Ctrl->L.minimum_given) G[0]->header->z_min = Ctrl->L.min;
		if (!Ctrl->L.maximum_given) G[0]->header->z_max = Ctrl->L.max;
	}
	else {
		Ctrl->L.min = G[0]->header->z_max;	/* This is just to double check G[k]->header->z_min, G[k]->header->z_max  */
		Ctrl->L.max = G[0]->header->z_min;
		for (k = 0; k < ngrd; k++) {	/* For each grid */
			gmt_M_grd_loop (GMT, G[k], row, col, ij) {
				if (gmt_M_is_fnan (G[k]->data[ij]))
					nfound++;
				else if (Ctrl->E.cdf) {
					pair[nxy].value    = G[k]->data[ij];
					pair[nxy++].weight = W->data[ij];
					wsum += W->data[ij];
				}
				else {
					if (G[k]->data[ij] < Ctrl->L.min) Ctrl->L.min = G[k]->data[ij];
					if (G[k]->data[ij] > Ctrl->L.max) Ctrl->L.max = G[k]->data[ij];
					mean += G[k]->data[ij];
					sd += G[k]->data[ij] * G[k]->data[ij];
				}
			}
		}
		G[0]->header->z_min = Ctrl->L.min;
		G[0]->header->z_max = Ctrl->L.max;
	}

	if (Ctrl->E.cdf) {
		gmt_free_grid (GMT, &W, true);	/* Done with the area weights grid */
		/* Sort observations on z */
		qsort (pair, nxy, sizeof (struct GMT_OBSERVATION), gmtlib_compare_observation);
		/* Compute normalized cumulative weights */
		scale = 1.0 / wsum;	/* Do avoid division later */
		wsum = 0.0;	/* Do this in double precision since GMT_OBSERVATION is just float */
		for (k = 0; k < nxy; k++) {	/* Build CDF from tiny to 1 */
			pair[k].weight *= scale;
			wsum += pair[k].weight;
			pair[k].weight = (gmt_grdfloat)wsum;
		}
		if (Ctrl->E.file) {	/* Save the CDF to file */
			uint64_t dim[4] = {1, 1, nxy, 2};
			struct GMT_DATASET *CDF = NULL;
			struct GMT_DATASEGMENT *S = NULL;
			if ((CDF = GMT_Create_Data (API, GMT_IS_DATASET, GMT_IS_POINT, 0, dim, NULL, NULL, 0, 0, NULL)) == NULL) {
				GMT_Report (API, GMT_MSG_ERROR, "Unable to allocate memory for CDF output.\n");
				Return (GMT_MEMORY_ERROR);
			}
			S = CDF->table[0]->segment[0];
			for (k = 0; k < nxy; k++) {
				S->data[GMT_X][k] = pair[k].value;
				S->data[GMT_Y][k] = pair[k].weight;
			}
			if (GMT_Write_Data (API, GMT_IS_DATASET, GMT_IS_FILE, GMT_IS_POINT, GMT_WRITE_NORMAL, NULL, Ctrl->E.file, CDF) != GMT_NOERROR) {
				GMT_Report (API, GMT_MSG_ERROR, "Unable to write CDF output.\n");
				Return (API->error);
			}
		}
	}

	if (Ctrl->E.active && Ctrl->E.levels == 0) {	/* Use existing CPT structure, just linearly change z */
		if ((Pout = GMT_Duplicate_Data (API, GMT_IS_PALETTE, GMT_DUPLICATE_ALLOC, Pin)) == NULL) return (API->error);
		if ((gmt_stretch_cpt (GMT, Pout, Ctrl->L.min, Ctrl->L.max)) == GMT_PARSE_ERROR)
			Return (GMT_RUNTIME_ERROR);
		if (Ctrl->I.mode & GMT_CPT_C_REVERSE)
			gmt_invert_cpt (GMT, Pout);	/* Also flip the colors */
		cpt_flags = 0;
		if (Ctrl->N.active) cpt_flags |= GMT_CPT_NO_BNF;	/* bit 0 controls if BFN will be written out */
		if (Ctrl->D.mode == 1) cpt_flags |= GMT_CPT_EXTEND_BNF;	/* bit 1 controls if BF will be set to equal bottom/top rgb value */
		if (Ctrl->F.active) Pout->model = Ctrl->F.model;
		if (Ctrl->F.cat) Pout->categorical = GMT_CPT_CATEGORICAL_VAL;
		if (write && GMT_Write_Data (API, GMT_IS_PALETTE, GMT_IS_FILE, GMT_IS_NONE, cpt_flags, NULL, Ctrl->Out.file, Pout) != GMT_NOERROR) {
			Return (API->error);
		}
		if (!write)
			gmt_save_current_cpt (GMT, Pout, cpt_flags);	/* Save for use by session, if modern */
		grd2cpt_free_the_grids (API, G, grdfile, ngrd);
		gmt_M_free (GMT, G);
		gmt_M_free (GMT, grdfile);

		Return (GMT_NOERROR);
	}

	ngood = nxyg - nfound;	/* This is the number of non-NaN points for the cdf function  */
	mean /= ngood;
	sd /= ngood;
	sd = sqrt (sd - mean * mean);
	if (gmt_M_is_verbose (GMT, GMT_MSG_WARNING)) {
		sprintf (format, "Mean and S.D. of data are %s %s\n",
		         GMT->current.setting.format_float_out, GMT->current.setting.format_float_out);
		GMT_Report (API, GMT_MSG_INFORMATION, format, mean, sd);
	}

	/* Decide how to make steps in z.  */
	if (Ctrl->T.active && Ctrl->T.mode == 0) {	/* Use predefined levels and interval */
		unsigned int i, j;

		Ctrl->E.levels = (G[0]->header->z_min < Ctrl->T.low) ? 1 : 0;
		Ctrl->E.levels += urint (floor((Ctrl->T.high - Ctrl->T.low)/Ctrl->T.inc)) + 1;
		if (G[0]->header->z_max > Ctrl->T.high) Ctrl->E.levels++;
		cdf_cpt = gmt_M_memory (GMT, NULL, Ctrl->E.levels, struct CDF_CPT);
		if (G[0]->header->z_min < Ctrl->T.low) {
			cdf_cpt[0].z = G[0]->header->z_min;
			cdf_cpt[1].z = Ctrl->T.low;
			i = 2;
		}
		else {
			cdf_cpt[0].z = Ctrl->T.low;
			i = 1;
		}
		j = (G[0]->header->z_max > Ctrl->T.high) ? Ctrl->E.levels - 1 : Ctrl->E.levels;
		while (i < j) {
			cdf_cpt[i].z = cdf_cpt[i-1].z + Ctrl->T.inc;
			i++;
		}
		if (j == Ctrl->E.levels-1) cdf_cpt[j].z = G[0]->header->z_max;
	}
	else if (Ctrl->S.active || (Ctrl->E.active && !Ctrl->E.cdf)) {	/* Make an equaldistant color map from G[k]->header->z_min to G[k]->header->z_max */
		double start, range;

		switch (Ctrl->S.kind) {
			case -1:
				start = -fabs (G[0]->header->z_min);
				break;
			case 1:
				start = -fabs (G[0]->header->z_max);
				break;
			case -2:
				start = -MIN (fabs (G[0]->header->z_min), fabs (G[0]->header->z_max));
				break;
			case 2:
				start = -MAX (fabs (G[0]->header->z_min), fabs (G[0]->header->z_max));
				break;
			default:
				start = G[0]->header->z_min;
				break;
		}
		range = (Ctrl->S.kind) ? 2.0 * fabs (start) : G[0]->header->z_max - G[0]->header->z_min;
		range *= (1.0 + GMT_CONV8_LIMIT);	/* To ensure the max grid values do not exceed the CPT limit due to round-off issues */
		start -= fabs (start) * GMT_CONV8_LIMIT;	/* To ensure the start of cpt is less than min value due to roundoff  */
		Ctrl->T.inc = range / (double)(Ctrl->E.levels - 1);
		cdf_cpt = gmt_M_memory (GMT, NULL, Ctrl->E.levels, struct CDF_CPT);
		for (j = 0; j < Ctrl->E.levels; j++) cdf_cpt[j].z = start + j * Ctrl->T.inc;
	}
	else if (Ctrl->E.cdf) {	/* Use the cumulative weighted distribution to issue the desired equal-area level boundaries */
		double dw = pair[nxy-1].weight / (Ctrl->E.levels - 1), p = 0.0, dp = 1.0 / (Ctrl->E.levels - 1);

		cdf_cpt = gmt_M_memory (GMT, NULL, Ctrl->E.levels, struct CDF_CPT);
		cdf_cpt[0].z = pair[0].value;
		wsum = dw;	p = dp;
		GMT_Report (API, GMT_MSG_INFORMATION, "Evaluated %d equidistant points on the cumulative density function:\n", Ctrl->E.levels);
		GMT_Report (API, GMT_MSG_INFORMATION, "z = %16g cdf(z) = %6.4f\n", cdf_cpt[0].z, 0.0);
		for (j = 1, k = 0; j < (Ctrl->E.levels - 1); j++) {
			while (k < nxy && pair[k].weight < wsum) k++;	/* k is the point with weight >= wsum; so a linear interpolation */
			cdf_cpt[j].z = pair[k-1].value + (wsum - pair[k-1].weight) * (pair[k].value - pair[k-1].value) / (pair[k].weight - pair[k-1].weight);
			GMT_Report (API, GMT_MSG_INFORMATION, "z = %16g cdf(z) = %6.4f\n", cdf_cpt[j].z, p);
			wsum += dw;	/* Next area boundary */
			p += dp;	/* Next CDF value */
		}
		cdf_cpt[Ctrl->E.levels-1].z = pair[nxy-1].value;
		GMT_Report (API, GMT_MSG_INFORMATION, "z = %16g cdf(z) = %6.4f\n", cdf_cpt[Ctrl->E.levels-1].z, 1.0);
		gmt_M_free (GMT, pair);
		/* Make sure we do not have slices with no z-range */
		p = 0.0;
		dp = GMT_CONV8_LIMIT * (cdf_cpt[Ctrl->E.levels-1].z - cdf_cpt[0].z);
		for (j = 1; j < (Ctrl->E.levels - 1); j++) {
			if (doubleAlmostEqualZero (cdf_cpt[j-1].z, cdf_cpt[j].z+p)) {
				GMT_Report (API, GMT_MSG_WARNING, "CDF is vertical, adding %g to have monotonic increasing z-values:\n", dp);
				p += dp;
				cdf_cpt[j].z += p;
			}
		}
	}
	else {	/* This is completely ad-hoc.  It chooses z based on equidistant steps [of 0.1 unless -Sn set] for a Gaussian CDF:  */
		double z_inc = 1.0 / (Ctrl->E.levels - 1);		/* Increment between selected points [0.1] */
		double zcrit_tail = gmt_zcrit (GMT, 1.0 - z_inc);	/* Get the +/- z-value containing bulk of distribution, with z_inc in each tail */
		cdf_cpt = gmt_M_memory (GMT, NULL, Ctrl->E.levels, struct CDF_CPT);
		if ((mean - zcrit_tail*sd) <= G[0]->header->z_min || (mean + zcrit_tail*sd) >= G[0]->header->z_max) {
			/* Adjust mean/std so that our critical locations are still inside the min/max of the data */
			mean = 0.5 * (G[0]->header->z_min + G[0]->header->z_max);
			sd = (G[0]->header->z_max - mean) / 1.5;	/* This factor of 1.5 probably needs to change since z_inc is no longer fixed at 0.1 */
			if (sd <= 0.0) {
				GMT_Report (API, GMT_MSG_ERROR, "Min and Max data values are equal.\n");
				gmt_M_free (GMT, cdf_cpt);
				Return (GMT_RUNTIME_ERROR);
			}
		}	/* End of stupid bug fix  */

		/* So we go in steps of z_inc in the Gaussian CDF except we start and stop at actual min/max */
		cdf_cpt[0].z = G[0]->header->z_min;
		for (j = 1; j < (Ctrl->E.levels - 1); j++) cdf_cpt[j].z = mean + gmt_zcrit (GMT, j *z_inc) * sd;
		cdf_cpt[Ctrl->E.levels-1].z = G[0]->header->z_max;
	}

	/* Get here when we are ready to go.  cdf_cpt[].z contains the sample points.  */

	if (gmt_M_is_verbose (GMT, GMT_MSG_INFORMATION)) sprintf (format, "z = %s and CDF(z) = %s\n", GMT->current.setting.format_float_out, GMT->current.setting.format_float_out);
	for (j = 0; j < Ctrl->E.levels; j++) {
		if (cdf_cpt[j].z <= G[0]->header->z_min)
			cdf_cpt[j].f = 0.0;
		else if (cdf_cpt[j].z >= G[0]->header->z_max)
			cdf_cpt[j].f = 1.0;
		else {
			nfound = 0;
			for (k = 0; k < ngrd; k++) {	/* For each grid */
				gmt_M_grd_loop (GMT, G[k], row, col, ij) {
					if (!gmt_M_is_fnan (G[k]->data[ij]) && G[k]->data[ij] <= cdf_cpt[j].z) nfound++;
				}
			}
			cdf_cpt[j].f = (double)(nfound-1)/(double)(ngood-1);
		}
		GMT_Report (API, GMT_MSG_INFORMATION, format, cdf_cpt[j].z, cdf_cpt[j].f);
	}

	/* Now the cdf function has been found.  We now resample the chosen CPT  */

	z = gmt_M_memory (GMT, NULL, Ctrl->E.levels, double);
	for (j = 0; j < Ctrl->E.levels; j++) z[j] = cdf_cpt[j].z;
	if (Ctrl->Q.mode == 2) for (j = 0; j < Ctrl->E.levels; j++) z[j] = d_log10 (GMT, z[j]);	/* Make log10(z) values for interpolation step */

	signed_levels = Ctrl->E.levels;
	Pout = gmt_sample_cpt (GMT, Pin, z, -signed_levels, Ctrl->Z.active, Ctrl->I.active, Ctrl->Q.mode, Ctrl->W.active);	/* -ve to keep original colors */

	/* Determine mode flags for output */
	cpt_flags = 0;
	if (Ctrl->N.active) cpt_flags |= GMT_CPT_NO_BNF;	/* bit 0 controls if BFN will be written out */
	if (Ctrl->D.mode == 1) cpt_flags |= GMT_CPT_EXTEND_BNF;	/* bit 1 controls if BF will be set to equal bottom/top rgb value */
	if (Ctrl->F.active) Pout->model = Ctrl->F.model;

	if (Ctrl->A.active) gmt_cpt_transparency (GMT, Pout, Ctrl->A.value, Ctrl->A.mode);	/* Set transparency */
	if (Ctrl->F.model & GMT_GRAY) cpt_flags = GMT_CPT_GRAY_SET;	/* Controls if final CPT should be converted to gray via YIQ */

	if (Ctrl->F.cat) {	/* Flag as a categorical CPT */
		if ((API->error = gmt_prepare_categorical_cpt (GMT, Ctrl->F.label, Ctrl->F.key, Pout)))
			Return (API->error);
	}

	if (write && GMT_Write_Data (API, GMT_IS_PALETTE, GMT_IS_FILE, GMT_IS_NONE, cpt_flags, NULL, Ctrl->Out.file, Pout) != GMT_NOERROR)
		error = API->error;

	if (!write)
		gmt_save_current_cpt (GMT, Pout, cpt_flags);	/* Save for use by session, if modern */

	gmt_M_free (GMT, cdf_cpt);
	gmt_M_free (GMT, z);
	if (error == GMT_NOERROR)
		error = grd2cpt_free_the_grids (API, G, grdfile, ngrd);
	else
		grd2cpt_free_the_grids (API, G, grdfile, ngrd);
	gmt_M_free (GMT, G);
	gmt_M_free (GMT, grdfile);

	Return ((error) ? error : GMT_NOERROR);
}