iniciando o projeto

framebuffer_simple.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdint.h>
+
+#define WIDTH 720
+#define HEIGHT 720
+#define BPP 4  // BGRA = 4 bytes per pixel
+
+typedef struct {
+    int fb_fd;
+    uint8_t *framebuffer;
+} FramebufferDemo;
+
+// Initialize framebuffer
+int fb_init(FramebufferDemo *fb) {
+    // Open framebuffer device
+    fb->fb_fd = open("/dev/fb0", O_RDWR);
+    if (fb->fb_fd < 0) {
+        fprintf(stderr, "Error: Cannot open framebuffer device /dev/fb0\n");
+        fprintf(stderr, "Make sure you have permissions (try running with sudo)\n");
+        return -1;
+    }
+    
+    // Allocate framebuffer memory
+    fb->framebuffer = (uint8_t*)malloc(WIDTH * HEIGHT * BPP);
+    if (!fb->framebuffer) {
+        fprintf(stderr, "Error: Cannot allocate framebuffer memory\n");
+        close(fb->fb_fd);
+        return -1;
+    }
+    
+    printf("Framebuffer opened successfully\n");
+    printf("Resolution: %dx%d, Format: BGRA\n", WIDTH, HEIGHT);
+    
+    return 0;
+}
+
+// Close framebuffer
+void fb_close(FramebufferDemo *fb) {
+    if (fb->framebuffer) {
+        free(fb->framebuffer);
+        fb->framebuffer = NULL;
+    }
+    if (fb->fb_fd >= 0) {
+        close(fb->fb_fd);
+        fb->fb_fd = -1;
+    }
+}
+
+// Set a pixel at (x, y) with BGRA color
+void set_pixel(FramebufferDemo *fb, int x, int y, uint8_t b, uint8_t g, uint8_t r, uint8_t a) {
+    if (x < 0 || x >= WIDTH || y < 0 || y >= HEIGHT) {
+        return;
+    }
+    
+    int offset = (y * WIDTH + x) * BPP;
+    fb->framebuffer[offset + 0] = b; // Blue
+    fb->framebuffer[offset + 1] = g; // Green
+    fb->framebuffer[offset + 2] = r; // Red
+    fb->framebuffer[offset + 3] = a; // Alpha
+}
+
+// Fill entire screen with a color
+void fill_screen(FramebufferDemo *fb, uint8_t b, uint8_t g, uint8_t r, uint8_t a) {
+    for (int y = 0; y < HEIGHT; y++) {
+        for (int x = 0; x < WIDTH; x++) {
+            set_pixel(fb, x, y, b, g, r, a);
+        }
+    }
+}
+
+// Draw a rectangle
+void draw_rectangle(FramebufferDemo *fb, int x, int y, int w, int h, 
+                   uint8_t b, uint8_t g, uint8_t r, uint8_t a) {
+    for (int dy = 0; dy < h; dy++) {
+        for (int dx = 0; dx < w; dx++) {
+            set_pixel(fb, x + dx, y + dy, b, g, r, a);
+        }
+    }
+}
+
+// Draw a circle
+void draw_circle(FramebufferDemo *fb, int cx, int cy, int radius, 
+                uint8_t b, uint8_t g, uint8_t r, uint8_t a) {
+    for (int y = -radius; y <= radius; y++) {
+        for (int x = -radius; x <= radius; x++) {
+            if (x * x + y * y <= radius * radius) {
+                set_pixel(fb, cx + x, cy + y, b, g, r, a);
+            }
+        }
+    }
+}
+
+// Update the framebuffer (write to /dev/fb0)
+void fb_update(FramebufferDemo *fb) {
+    if (fb->fb_fd < 0) {
+        fprintf(stderr, "Error: Framebuffer not opened\n");
+        return;
+    }
+    
+    // Seek to beginning of framebuffer
+    lseek(fb->fb_fd, 0, SEEK_SET);
+    
+    // Write framebuffer data
+    ssize_t written = write(fb->fb_fd, fb->framebuffer, WIDTH * HEIGHT * BPP);
+    if (written < 0) {
+        fprintf(stderr, "Error writing to framebuffer\n");
+    }
+}
+
+int main(int argc, char *argv[]) {
+    FramebufferDemo fb = {0};
+    
+    if (fb_init(&fb) < 0) {
+        return 1;
+    }
+    
+    printf("Drawing demo graphics...\n");
+    
+    // Fill screen with black
+    fill_screen(&fb, 0, 0, 0, 255);
+    
+    // Draw a red rectangle
+    draw_rectangle(&fb, 100, 100, 200, 150, 0, 0, 255, 255);
+    
+    // Draw a green circle
+    draw_circle(&fb, 500, 200, 80, 0, 255, 0, 255);
+    
+    // Draw a blue rectangle
+    draw_rectangle(&fb, 200, 400, 300, 100, 255, 0, 0, 255);
+    
+    // Draw a yellow circle
+    draw_circle(&fb, 360, 360, 100, 0, 255, 255, 255);
+    
+    // Update the framebuffer
+    fb_update(&fb);
+    
+    printf("Graphics drawn! Press Enter to clear and exit...\n");
+    getchar();
+    
+    // Clear screen before exit
+    fill_screen(&fb, 0, 0, 0, 255);
+    fb_update(&fb);
+    
+    printf("Done!\n");
+    
+    fb_close(&fb);
+    return 0;
+}