initial commit

.gitignore

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+main
+image.ppm

Makefile

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+.PHONY := run
+
+run: main
+	./main
+
+main: main.c Makefile
+	gcc -o main main.c -O3 -g

README.md

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+# The Four Programming Questions from Computer Enhance
+
+My solutions for the questions from this post: https://www.computerenhance.com/p/the-four-programming-questions-from
+
+These solution might not be the best, but they are mine ant I like them.

main.c

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+#include <math.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+
+// Question 1:
+void copy_rect(
+		char *buffer_a, int pitch_a,
+		char *buffer_b, int pitch_b,
+		int from_min_x, int from_min_y,
+		int from_max_x, int from_max_y,
+		int   to_min_x, int   to_min_y
+	) {
+
+	for (int y = 0; y < (from_max_y - from_min_y); y++) {
+		for (int x = 0; x < (from_max_x - from_min_x); x++) {
+			int from_idx = (y + from_min_y) * pitch_a + (x + from_min_x);
+			int to_idx   = (y + to_min_y  ) * pitch_b + (x + to_min_x  );
+
+			buffer_b[to_idx] = buffer_a[from_idx];
+		}
+	}
+}
+
+// Question 2:
+void copy_string(char *from, char *to) {
+	int i = 0;
+	while (from[i] != 0) {
+		to[i] = from[i];
+		i++;
+	}
+	to[i] = 0;
+}
+
+// Question 3:
+bool contains_color(char unsigned pixel, char unsigned color) {
+	char mask = (color << 6) | (color << 4) | (color << 2) | color;
+	char masked = ~(pixel ^ mask);
+	char masked2 = masked & (masked << 1);
+	return (masked2 & 0b10101010) != 0;
+}
+
+// Question 4:
+struct Image {
+	bool *data;
+	int width, height;
+};
+
+void write_image_ppm(char *filename, struct Image *image) {
+	FILE* f = fopen(filename, "w");
+	char header[64];
+	int header_size = snprintf(header, sizeof(header), "P1\n%d %d\n", image->width, image->height);
+	fwrite(header, sizeof(char), header_size, f);
+	for (int i = 0; i < image->width * image->height; i++) {
+		char *symbol = image->data[i] ? "1" : "0";
+		fwrite(symbol, sizeof(char), 1, f);
+	}
+	fclose(f);
+}
+
+void plot(struct Image *image, int x, int y) {
+	if ((0 <= x && x < image->width) && (0 <= y && y < image->height)) {
+		int idx = y * image->width + x;
+		image->data[idx] = true;
+	}
+}
+
+void outline_circle(struct Image *image, int cx, int cy, int radius) {
+	int mid_point = ceil(radius/sqrt(2));
+
+	int oy = -radius;
+	for (int ox = 0; ox < mid_point; ox++) {
+		if (ox*ox + oy*oy >= radius*radius) {
+			oy++;
+		}
+
+		plot(image, cx+ox, cy+oy);
+		plot(image, cx-ox, cy+oy);
+		plot(image, cx+ox, cy-oy);
+		plot(image, cx-ox, cy-oy);
+		plot(image, cx+oy, cy+ox);
+		plot(image, cx-oy, cy+ox);
+		plot(image, cx+oy, cy-ox);
+		plot(image, cx-oy, cy-ox);
+	}
+}
+
+int main() {
+	int image_width = 100;
+	int image_height = 100;
+	bool image_data[image_width * image_height];
+	memset(image_data, false, sizeof(bool) * image_width * image_height);
+	struct Image image = {
+		.data = image_data,
+		.width = image_width,
+		.height = image_height
+	};
+
+	for (int i = 8; i < 50; i+=10) {
+		outline_circle(&image, 50, 50, i);
+	}
+	write_image_ppm("image.ppm", &image);
+
+	return 0;
+}