从C中在Linux上的framebuffer上绘制文本,需要使用一些基本的库和函数来实现。以下是一个简单的示例,展示了如何在Linux framebuffer上绘制文本。
首先,需要安装必要的库和头文件:
sudo apt-get install libsdl2-dev
然后,编写一个简单的C程序来绘制文本:
#include <SDL2/SDL.h>
#include <SDL2/SDL_ttf.h>
#include<stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <stdint.h>
#define FBDEV "/dev/fb0"
#define FONT_PATH "/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf"
int main(int argc, char *argv[])
{
int fbfd = 0;
struct fb_var_screeninfo vinfo;
struct fb_fix_screeninfo finfo;
char *fbp = 0;
long int screensize = 0;
int x = 0, y = 0;
int font_size = 24;
SDL_Window *window;
SDL_Renderer *renderer;
SDL_Texture *texture;
SDL_Surface *surface;
TTF_Font *font;
SDL_Color color = {255, 255, 255};
SDL_Rect dst_rect = {0, 0, 0, 0};
const char *text = "Hello, world!";
// 初始化SDL
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
exit(1);
}
// 初始化TTF
if (TTF_Init() < 0) {
printf("TTF could not initialize! SDL_Error: %s\n", SDL_GetError());
exit(1);
}
// 打开framebuffer设备
fbfd = open(FBDEV, O_RDWR);
if (fbfd == -1) {
perror("Error: cannot open framebuffer device");
exit(1);
}
// 获取屏幕信息
if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) {
perror("Error reading fixed information");
exit(1);
}
if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
perror("Error reading variable information");
exit(1);
}
// 计算屏幕大小
screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
// 映射到用户内存
fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
if (fbp == (char *)-1) {
perror("Error: failed to map framebuffer device to memory");
exit(1);
}
// 创建SDL窗口
window = SDL_CreateWindow("Draw Text on Framebuffer", 0, 0, vinfo.xres, vinfo.yres, SDL_WINDOW_FULLSCREEN_DESKTOP);
if (!window) {
fprintf(stderr, "SDL_CreateWindow failed: %s\n", SDL_GetError());
exit(1);
}
// 创建渲染器
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
if (!renderer) {
fprintf(stderr, "SDL_CreateRenderer failed: %s\n", SDL_GetError());
exit(1);
}
// 加载字体
font = TTF_OpenFont(FONT_PATH, font_size);
if (!font) {
fprintf(stderr, "TTF_OpenFont failed: %s\n", TTF_GetError());
exit(1);
}
// 创建文本纹理
surface = TTF_RenderText_Blended(font, text, color);
if (!surface) {
fprintf(stderr, "TTF_RenderText_Blended failed: %s\n", TTF_GetError());
exit(1);
}
// 创建纹理
texture = SDL_CreateTextureFromSurface(renderer, surface);
if (!texture) {
fprintf(stderr, "SDL_CreateTextureFromSurface failed: %s\n", SDL_GetError());
exit(1);
}
// 设置绘制位置
dst_rect.x = x;
dst_rect.y = y;
dst_rect.w = surface->w;
dst_rect.h = surface->h;
// 清除屏幕
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
SDL_RenderClear(renderer);
// 绘制文本
SDL_RenderCopy(renderer, texture, NULL, &dst_rect);
SDL_RenderPresent(renderer);
// 等待用户退出
SDL_Event event;
while (1) {
if (SDL_PollEvent(&event)) {
if (event.type == SDL_QUIT) {
break;
}
}
}
// 释放资源
SDL_DestroyTexture(texture);
SDL_FreeSurface(surface);
TTF_CloseFont(font);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
TTF_Quit();
SDL_Quit();
munmap(fbp, screensize);
close(fbfd
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