✨ Add terminal support

meson.build

@@ -4,7 +4,7 @@ project('Foto', 'c',
   default_options: ['warning_level=3'])
 
 # define source files
-src = files('src/main.c', 'src/arg.c', 'src/arg.h', 'src/image.c', 'src/image.h', 'src/util.c', 'src/util.h')
+src = files('src/main.c', 'src/arg.c', 'src/arg.h', 'src/image.c', 'src/image.h', 'src/util.c', 'src/util.h', 'src/term.c', 'src/term.h', 'src/color.c', 'src/color.h')
 
 # define project metadata
 url = 'https://github.com/mekb-turtle/Foto'
@@ -20,4 +20,5 @@ add_project_arguments(
 exe = executable('foto', sources: src, install: true, dependencies: [
   dependency('SDL2'),
   dependency('SDL2_image'),
+  dependency('ncurses')
 ])

src/arg.c

@@ -6,8 +6,8 @@
 
 #include <SDL2/SDL.h>
 
-#include "./arg.h"
-#include "./util.h"
+#include "arg.h"
+#include "util.h"
 
 bool is_num(char *str) {
 	// locale-aware

src/color.c

@@ -0,0 +1,69 @@
+#include "color.h"
+
+#define SQ(x) ((x) * (x))
+
+size_t closest_color(struct color color, struct color *color_table, size_t color_len) {
+	size_t closest;
+	uint32_t closest_dist = -1; // max value
+	for (size_t i = 0; i < color_len; ++i) {
+		uint32_t dist = SQ(color.r - color_table[i].r) + SQ(color.g - color_table[i].g) + SQ(color.b - color_table[i].b);
+		if (dist < closest_dist) {
+			closest = i;
+			closest_dist = dist;
+		}
+	}
+	return closest;
+}
+
+#define VAL(n) ((n) == 0 ? 0 : 40 * (n) + 55) // 0, 95, 135, 175, 215, 255
+
+uint8_t rgb_to_8bit(struct color color) {
+	static struct color color_table[240];
+	static bool color_table_init = false;
+	if (!color_table_init) {
+		color_table_init = true;
+		uint8_t i = 0;
+		struct color color;
+		color.a = 0xff;
+
+		// fill colors (6^3)
+		for (color.r = 0; color.r < 6; ++color.r)
+			for (color.g = 0; color.g < 6; ++color.g)
+				for (color.b = 0; color.b < 6; ++color.b, ++i) {
+					color_table[i] = (struct color){
+					        .r = VAL(color.r),
+					        .g = VAL(color.g),
+					        .b = VAL(color.b),
+					};
+				}
+		// fill grayscale (24)
+		for (color.r = 8; color.r < 238; color.r += 10, ++i) {
+			color.b = color.g = color.r;
+			color_table[i] = color;
+		}
+	}
+
+	// find closest color (16-255)
+	return closest_color(color, color_table, 240) + 16;
+}
+
+uint8_t rgb_to_4bit(struct color color) {
+	static struct color color_table[16];
+	static bool color_table_init = false;
+	if (!color_table_init) {
+		color_table_init = true;
+		for (uint8_t i = 0; i < 16; ++i) {
+			color_table[i] = (struct color){.a = 0xff};
+			uint8_t n = (i & 0x8) ? 0xff : 0x80;
+			// dynamically generate color table
+			color_table[i].r = (i & 0x1) ? n : 0x00;
+			color_table[i].g = (i & 0x2) ? n : 0x00;
+			color_table[i].b = (i & 0x4) ? n : 0x00;
+		};
+		color_table[8] = color_table[7];
+		color_table[7] = (struct color){{{0xc0, 0xc0, 0xc0, 0xff}}};
+	}
+
+	// find closest color (0-15)
+	return closest_color(color, color_table, 16);
+}

src/color.h

@@ -0,0 +1,21 @@
+#ifndef COLOR_H
+#define COLOR_H
+#include <stdbool.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <SDL2/SDL.h>
+
+struct color {
+	union {
+		struct {
+			uint8_t r, g, b, a;
+		};
+		uint32_t u32;
+	};
+};
+
+size_t closest_color(struct color color, struct color *color_table, size_t color_len);
+uint8_t rgb_to_8bit(struct color color);
+uint8_t rgb_to_4bit(struct color color);
+
+#endif

src/image.c

@@ -5,8 +5,8 @@
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_image.h>
 
-#include "./util.h"
-#include "./image.h"
+#include "util.h"
+#include "image.h"
 
 // get file pointer from filename
 FILE *open_file(char *filename) {