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#include <png.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include "pngwriter.h"
/* Datatype for RGB pixel */
typedef struct {
uint8_t red;
uint8_t green;
uint8_t blue;
} pixel_t;
void cmap(double value, const double scaling, const double maxval,
pixel_t *pix);
static int heat_colormap[256][3] = {
{59, 76, 192}, {59, 76, 192}, {60, 78, 194}, {61, 80, 195},
{62, 81, 197}, {64, 83, 198}, {65, 85, 200}, {66, 87, 201},
{67, 88, 203}, {68, 90, 204}, {69, 92, 206}, {71, 93, 207},
{72, 95, 209}, {73, 97, 210}, {74, 99, 211}, {75, 100, 213},
{77, 102, 214}, {78, 104, 215}, {79, 105, 217}, {80, 107, 218},
{82, 109, 219}, {83, 110, 221}, {84, 112, 222}, {85, 114, 223},
{87, 115, 224}, {88, 117, 225}, {89, 119, 227}, {90, 120, 228},
{92, 122, 229}, {93, 124, 230}, {94, 125, 231}, {96, 127, 232},
{97, 129, 233}, {98, 130, 234}, {100, 132, 235}, {101, 133, 236},
{102, 135, 237}, {103, 137, 238}, {105, 138, 239}, {106, 140, 240},
{107, 141, 240}, {109, 143, 241}, {110, 144, 242}, {111, 146, 243},
{113, 147, 244}, {114, 149, 244}, {116, 150, 245}, {117, 152, 246},
{118, 153, 246}, {120, 155, 247}, {121, 156, 248}, {122, 157, 248},
{124, 159, 249}, {125, 160, 249}, {127, 162, 250}, {128, 163, 250},
{129, 164, 251}, {131, 166, 251}, {132, 167, 252}, {133, 168, 252},
{135, 170, 252}, {136, 171, 253}, {138, 172, 253}, {139, 174, 253},
{140, 175, 254}, {142, 176, 254}, {143, 177, 254}, {145, 179, 254},
{146, 180, 254}, {147, 181, 255}, {149, 182, 255}, {150, 183, 255},
{152, 185, 255}, {153, 186, 255}, {154, 187, 255}, {156, 188, 255},
{157, 189, 255}, {158, 190, 255}, {160, 191, 255}, {161, 192, 255},
{163, 193, 255}, {164, 194, 254}, {165, 195, 254}, {167, 196, 254},
{168, 197, 254}, {169, 198, 254}, {171, 199, 253}, {172, 200, 253},
{173, 201, 253}, {175, 202, 252}, {176, 203, 252}, {177, 203, 252},
{179, 204, 251}, {180, 205, 251}, {181, 206, 250}, {183, 207, 250},
{184, 207, 249}, {185, 208, 249}, {186, 209, 248}, {188, 209, 247},
{189, 210, 247}, {190, 211, 246}, {191, 211, 246}, {193, 212, 245},
{194, 213, 244}, {195, 213, 243}, {196, 214, 243}, {198, 214, 242},
{199, 215, 241}, {200, 215, 240}, {201, 216, 239}, {202, 216, 239},
{204, 217, 238}, {205, 217, 237}, {206, 217, 236}, {207, 218, 235},
{208, 218, 234}, {209, 218, 233}, {210, 219, 232}, {211, 219, 231},
{212, 219, 230}, {214, 220, 229}, {215, 220, 228}, {216, 220, 227},
{217, 220, 225}, {218, 220, 224}, {219, 220, 223}, {220, 221, 222},
{221, 221, 221}, {222, 220, 219}, {223, 220, 218}, {224, 219, 216},
{225, 219, 215}, {226, 218, 214}, {227, 218, 212}, {228, 217, 211},
{229, 216, 209}, {230, 216, 208}, {231, 215, 206}, {232, 215, 205},
{233, 214, 203}, {233, 213, 202}, {234, 212, 200}, {235, 212, 199},
{236, 211, 197}, {237, 210, 196}, {237, 209, 194}, {238, 208, 193},
{239, 208, 191}, {239, 207, 190}, {240, 206, 188}, {240, 205, 187},
{241, 204, 185}, {242, 203, 183}, {242, 202, 182}, {243, 201, 180},
{243, 200, 179}, {243, 199, 177}, {244, 198, 176}, {244, 197, 174},
{245, 196, 173}, {245, 195, 171}, {245, 194, 169}, {246, 193, 168},
{246, 192, 166}, {246, 190, 165}, {246, 189, 163}, {247, 188, 161},
{247, 187, 160}, {247, 186, 158}, {247, 184, 157}, {247, 183, 155},
{247, 182, 153}, {247, 181, 152}, {247, 179, 150}, {247, 178, 149},
{247, 177, 147}, {247, 175, 146}, {247, 174, 144}, {247, 172, 142},
{247, 171, 141}, {247, 170, 139}, {247, 168, 138}, {247, 167, 136},
{247, 165, 135}, {246, 164, 133}, {246, 162, 131}, {246, 161, 130},
{246, 159, 128}, {245, 158, 127}, {245, 156, 125}, {245, 155, 124},
{244, 153, 122}, {244, 151, 121}, {243, 150, 119}, {243, 148, 117},
{242, 147, 116}, {242, 145, 114}, {241, 143, 113}, {241, 142, 111},
{240, 140, 110}, {240, 138, 108}, {239, 136, 107}, {239, 135, 105},
{238, 133, 104}, {237, 131, 102}, {237, 129, 101}, {236, 128, 99},
{235, 126, 98}, {235, 124, 96}, {234, 122, 95}, {233, 120, 94},
{232, 118, 92}, {231, 117, 91}, {230, 115, 89}, {230, 113, 88},
{229, 111, 86}, {228, 109, 85}, {227, 107, 84}, {226, 105, 82},
{225, 103, 81}, {224, 101, 79}, {223, 99, 78}, {222, 97, 77},
{221, 95, 75}, {220, 93, 74}, {219, 91, 73}, {218, 89, 71},
{217, 87, 70}, {215, 85, 69}, {214, 82, 67}, {213, 80, 66},
{212, 78, 65}, {211, 76, 64}, {210, 74, 62}, {208, 71, 61},
{207, 69, 60}, {206, 67, 59}, {204, 64, 57}, {203, 62, 56},
{202, 59, 55}, {200, 57, 54}, {199, 54, 53}, {198, 52, 51},
{196, 49, 50}, {195, 46, 49}, {193, 43, 48}, {192, 40, 47},
{191, 37, 46}, {189, 34, 44}, {188, 30, 43}, {186, 26, 42},
{185, 22, 41}, {183, 17, 40}, {182, 11, 39}, {180, 4, 38}
};
/*
* Save the two dimensional array as a png image
* Arguments:
* double *data - pointer to an array of nx * ny values
* int nx - number of COLUMNS to be written
* int ny - number of ROWS to be written
* char *fname - name of the picture
* char lang - either 'c' or 'f' denoting the memory
* layout. That is, if 'f' is given, then rows
* and columns are swapped.
*/
int save_png(double *data, const int height, const int width,
const char *fname, const char lang)
{
FILE *fp;
png_structp pngstruct_ptr = NULL;
png_infop pnginfo_ptr = NULL;
png_byte **row_pointers = NULL;
int i, j;
/* Default return status is failure */
int status = -1;
int pixel_size = 3;
int depth = 8;
/* Open the file and initialize the png library.
* Note that in error cases we jump to clean up
* parts in the end of this function using goto. */
fp = fopen(fname, "wb");
if (fp == NULL) {
goto fopen_failed;
}
pngstruct_ptr =
png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (pngstruct_ptr == NULL) {
goto pngstruct_create_failed;
}
pnginfo_ptr = png_create_info_struct(pngstruct_ptr);
if (pnginfo_ptr == NULL) {
goto pnginfo_create_failed;
}
if (setjmp(png_jmpbuf(pngstruct_ptr))) {
goto setjmp_failed;
}
png_set_IHDR(pngstruct_ptr, pnginfo_ptr, (size_t) width,
(size_t) height, depth, PNG_COLOR_TYPE_RGB,
PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
row_pointers = png_malloc(pngstruct_ptr, height * sizeof(png_byte *));
for (i = 0; i < height; i++) {
png_byte *row = png_malloc(pngstruct_ptr,
sizeof(uint8_t) * width * pixel_size);
row_pointers[i] = row;
/* Branch according to the memory layout */
if (lang == 'c' || lang == 'C') {
for (j = 0; j < width; j++) {
pixel_t pixel;
/* Scale the values so that values between 0 and
* 100 degrees are mapped to values between 0 and 255 */
cmap(data[j + i * width], 2.55, 0.0, &pixel);
*row++ = pixel.red;
*row++ = pixel.green;
*row++ = pixel.blue;
}
} else if (lang == 'f' || lang == 'F') {
for (j = 0; j < width; j++) {
pixel_t pixel;
cmap(data[i + j * height], 2.55, 0.0, &pixel);
*row++ = pixel.red;
*row++ = pixel.green;
*row++ = pixel.blue;
}
} else {
fprintf(stderr, "Unknown memory order %c for pngwriter!\n", lang);
exit(EXIT_FAILURE);
}
}
png_init_io(pngstruct_ptr, fp);
png_set_rows(pngstruct_ptr, pnginfo_ptr, row_pointers);
png_write_png(pngstruct_ptr, pnginfo_ptr,
PNG_TRANSFORM_IDENTITY, NULL);
status = 0;
for (i = 0; i < height; i++) {
png_free(pngstruct_ptr, row_pointers[i]);
}
png_free(pngstruct_ptr, row_pointers);
/* Cleanup with labels */
setjmp_failed:
pnginfo_create_failed:
png_destroy_write_struct(&pngstruct_ptr, &pnginfo_ptr);
pngstruct_create_failed:
fclose(fp);
fopen_failed:
return status;
}
/*
* This routine sets the RGB values for the pixel_t structure using
* the colormap data heat_colormap. If the value is outside the
* acceptable png values 0, 255 blue or red color is used instead.
*/
void cmap(double value, const double scaling, const double offset,
pixel_t *pix)
{
int ival;
ival = (int)(value * scaling + offset);
if (ival < 0) { /* Colder than colorscale, substitute blue */
pix->red = 0;
pix->green = 0;
pix->blue = 255;
} else if (ival > 255) {
pix->red = 255; /* Hotter than colormap, substitute red */
pix->green = 0;
pix->blue = 0;
} else {
pix->red = heat_colormap[ival][0];
pix->green = heat_colormap[ival][1];
pix->blue = heat_colormap[ival][2];
}
}