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Bogdanov_map.png (489 × 375 pixels, file size: 78 KB, MIME type: image/png)

Summary

Description
English: Bogdanov map  : with e=0, k=1.2, m=0
Date
Source Own work
Author Claudio Rocchini

Source code

#include <stdio.h>
#include <stdlib.h>
#include <vector>

int main() {
	const int dimx = 1024;		/* Image dimension */
	const int dimy = 1024;

	std::vector<size_t> I(dimx * dimy);
	for (int i = 0; i < dimx * dimy; ++i) I[i] = 0;

	const double e = 0;			/* brith and grow */
	const double k = 1.2;		/* Discretization */
	const double m = 0;			/* stability */
	const double step = 0.03;	/* Initial point step */

	for (double oy = -1.0; oy <= 1.0; oy += step) {
		for (double ox = -0.7; ox <= 1.3; ox += step) {
			if (ox == 0 || oy == 0) continue;			/* Avoid origin */
			double x = ox;
			double y = oy;
			for (size_t q = 0; q < 100000; ++q) {
				y = y + e * y + k * x * (x - 1) + m * x * y;
				x = x + y;
				if (fabs(x) > 2 || fabs(y) > 2) break;	/* the map diverge */
				double imx = (x - 0.3) * dimx / 2 + dimx / 2;
				double imy =  y        * dimy / 2 + dimy / 2;
				if (fabs(x) > 1e-6 || fabs(y) > 1e-6) {	/* Avoid origin */
					int ix = int(imx + 0.5);
					int iy = int(imy + 0.5);
					if (ix >= 0 && ix < dimx && iy >= 0 && iy < dimy)
						I[size_t(dimx) * (dimy - 1 - iy) + ix] ++;
				}
			}
		}
	}

	size_t maxd = I[0];			/* Compute max frequency */
	for (int i = 0; i < dimx * dimy; ++i)
		if (maxd < I[i]) maxd = I[i];

	FILE* fo = fopen("c:\\temp\\bogdanov_map2.pgm", "wb");
	fprintf(fo, "P5\n%d %d\n255\n", dimx, dimy);
	for (int i = 0; i < dimx * dimy; ++i) {
		int v = I[i] == 0 ? 0 : int(32 + (256 - 32) * I[i] / maxd + 0.5); if (v > 255) v = 255;
		unsigned char b = 255 - (unsigned char)v;
		fwrite(&b, 1, 1, fo);
	}
	fclose(fo);
	return 0;
}

Licensing

I, the copyright holder of this work, hereby publish it under the following license:
w:en:Creative Commons
attribution share alike
This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
You are free:
  • to share – to copy, distribute and transmit the work
  • to remix – to adapt the work
Under the following conditions:
  • attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
  • share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.

Captions

Example of Bogdanov map, with e=0, k=1.2, m=0

Items portrayed in this file

depicts

13 May 2020

image/png

8e545f7434065bbad248ba7bc4e9d95cb5b0e1b3

79,805 byte

375 pixel

489 pixel

File history

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Date/TimeThumbnailDimensionsUserComment
current12:03, 13 May 2020Thumbnail for version as of 12:03, 13 May 2020489 × 375 (78 KB)RocchiniUploaded own work with UploadWizard

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