json_color_out.c

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/*!
 * \file lib/raster/json_color_out.c
 *
 * \brief Raster Library - Print color table in json format
 *
 * (C) 2010-2024 by the GRASS Development Team
 *
 * This program is free software under the GNU General Public
 * License (>=v2). Read the file COPYING that comes with GRASS
 * for details.
 *
 * \author Nishant Bansal
 */
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#include <grass/gis.h>
#include <grass/colors.h>
#include <grass/gjson.h>
#include <grass/glocale.h>
#include <grass/raster.h>
 
/*!
   \brief Closes the file if it is not stdout.
 
   \param fp file where to print color table rules
 */
static void close_file(FILE *fp)
{
    if (fp != stdout)
        fclose(fp);
}
 
/*!
   \brief Writes a JSON rule for a specific color entry.
 
   \param val pointer to the DCELL value
   \param min,max minimum and maximum value for percentage output (used only
           when \p perc is non-zero)
   \param r red component of RGB color
   \param g green component of RGB color
   \param b blue component of RGB color
   \param root_array pointer to the JSON array
   \param perc TRUE for percentage output
   \param clr_frmt color format to be used (RBG, HEX, HSV, TRIPLET).
   \param fp file where to print color table rules
   \param root_value pointer to json value
 */
static void write_json_rule(DCELL *val, DCELL *min, DCELL *max, int r, int g,
                            int b, G_JSON_Array *root_array, int perc,
                            ColorFormat clr_frmt, FILE *fp,
                            G_JSON_Value *root_value)
{
    static DCELL v0;
    static int r0 = -1, g0 = -1, b0 = -1;
 
    // Skip writing if the current color is the same as the last one
    if (v0 == *val && r0 == r && g0 == g && b0 == b)
        return;
    // Update last processed values
    v0 = *val, r0 = r, g0 = g, b0 = b;
 
    G_JSON_Value *color_value = G_json_value_init_object();
    if (color_value == NULL) {
        G_json_value_free(root_value);
        close_file(fp);
        G_fatal_error(_("Failed to initialize JSON object. Out of memory?"));
    }
    G_JSON_Object *color_object = G_json_object(color_value);
 
    // Set the value as a percentage if requested, otherwise set it as-is
    if (perc)
        G_json_object_set_number(color_object, "value",
                                 100 * (*val - *min) / (*max - *min));
    else
        G_json_object_set_number(color_object, "value", *val);
 
    char color_str[COLOR_STRING_LENGTH];
    G_color_to_str(r, g, b, clr_frmt, color_str);
    G_json_object_set_string(color_object, "color", color_str);
 
    G_json_array_append_value(root_array, color_value);
}
 
/*!
   \brief Print color table in JSON format
 
   \param colors pointer to Colors structure
   \param min,max minimum and maximum value for percentage output (used only
           when \p perc is non-zero)
   \param fp file where to print color table rules
   \param perc TRUE for percentage output
   \param clr_frmt color format to be used (RBG, HEX, HSV, TRIPLET).
 */
void Rast_print_json_colors(struct Colors *colors, DCELL min, DCELL max,
                            FILE *fp, int perc, ColorFormat clr_frmt)
{
    G_JSON_Value *root_value = G_json_value_init_object();
    if (root_value == NULL) {
        close_file(fp);
        G_fatal_error(_("Failed to initialize JSON object. Out of memory?"));
    }
    G_JSON_Object *root_object = G_json_object(root_value);
 
    G_JSON_Value *table_value = G_json_value_init_array();
    if (table_value == NULL) {
        close_file(fp);
        G_fatal_error(_("Failed to initialize JSON array. Out of memory?"));
    }
    G_JSON_Array *table_array = G_json_array(table_value);
 
    char color_str[COLOR_STRING_LENGTH];
 
    if (colors->version < 0) {
        /* 3.0 format */
        CELL lo, hi;
 
        // Retrieve the integer color range
        Rast_get_c_color_range(&lo, &hi, colors);
 
        for (int i = lo; i <= hi; i++) {
            unsigned char r, g, b, set;
            DCELL val = (DCELL)i;
 
            // Look up the color for the current value and write JSON rule
            Rast_lookup_c_colors(&i, &r, &g, &b, &set, 1, colors);
            write_json_rule(&val, &min, &max, r, g, b, table_array, perc,
                            clr_frmt, fp, table_value);
        }
    }
    else {
        // Get the count of floating-point color rules
        int count = Rast_colors_count(colors);
 
        for (int i = 0; i < count; i++) {
            DCELL val1, val2;
            unsigned char r1, g1, b1, r2, g2, b2;
 
            // Retrieve the color rule values and their respective RGB colors
            Rast_get_fp_color_rule(&val1, &r1, &g1, &b1, &val2, &r2, &g2, &b2,
                                   colors, count - 1 - i);
 
            // write JSON rule
            write_json_rule(&val1, &min, &max, r1, g1, b1, table_array, perc,
                            clr_frmt, fp, table_value);
            write_json_rule(&val2, &min, &max, r2, g2, b2, table_array, perc,
                            clr_frmt, fp, table_value);
        }
    }
 
    // Add the color table to the root object
    G_json_object_set_value(root_object, "table", table_value);
 
    //  Add special color entries for "null" and "default" values
    {
        int r, g, b;
 
        // Get RGB color for null values and create JSON entry
        Rast_get_null_value_color(&r, &g, &b, colors);
        G_color_to_str(r, g, b, clr_frmt, color_str);
        G_json_object_set_string(root_object, "nv", color_str);
 
        // Get RGB color for default values and create JSON entry
        Rast_get_default_color(&r, &g, &b, colors);
        G_color_to_str(r, g, b, clr_frmt, color_str);
        G_json_object_set_string(root_object, "default", color_str);
    }
 
    // Serialize JSON array to a string and print to the file
    char *json_string = G_json_serialize_to_string_pretty(root_value);
    if (!json_string) {
        G_json_value_free(root_value);
        close_file(fp);
        G_fatal_error(_("Failed to serialize JSON to pretty format."));
    }
 
    fputs(json_string, fp);
 
    G_json_free_serialized_string(json_string);
    G_json_value_free(root_value);
 
    close_file(fp);
}