在 LCD 上表现 png 图片-I.MX6U嵌入式Linux C应用编程学习笔记基于正点原子 - ToB企服应用市场:ToB评测及商务社交产业平台

exit(0);

复制代码

- 验证
-
- libpng 设置错误返回点
- 错误处理机制：

复制代码

- 错误返回点设置：

复制代码

- 错误处理流程：

复制代码

- /* 设置错误返回点 */

复制代码

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <string.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <png.h>
static int width; //LCD X分辨率
static int height; //LCD Y分辨率
static unsigned short *screen_base = NULL; //映射后的显存基地址
static unsigned long line_length; //LCD一行的长度（字节为单位）
static unsigned int bpp; //像素深度bpp
static int show_png_image(const char *path)
{
png_structp png_ptr = NULL;
png_infop info_ptr = NULL;
FILE *png_file = NULL;
unsigned short *fb_line_buf = NULL; //行缓冲区:用于存储写入到LCD显存的一行数据
unsigned int min_h, min_w;
unsigned int valid_bytes;
unsigned int image_h, image_w;
png_bytepp row_pointers = NULL;
int i, j, k;
/* 打开png文件 */
png_file = fopen(path, "r"); //以只读方式打开
if (NULL == png_file) {
perror("fopen error");
return -1;
}
/* 分配和初始化png_ptr、info_ptr */
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (!png_ptr) {
fclose(png_file);
return -1;
}
info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr) {
png_destroy_read_struct(&png_ptr, NULL, NULL);
fclose(png_file);
return -1;
}
/* 设置错误返回点 */
if (setjmp(png_jmpbuf(png_ptr))) {
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
fclose(png_file);
return -1;
}
/* 指定数据源 */
png_init_io(png_ptr, png_file);
/* 读取png文件 */
png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_STRIP_ALPHA, NULL);
image_h = png_get_image_height(png_ptr, info_ptr);
image_w = png_get_image_width(png_ptr, info_ptr);
printf("分辨率: %d*%d\n", image_w, image_h);
/* 判断是不是RGB888 */
if ((8 != png_get_bit_depth(png_ptr, info_ptr)) &&
(PNG_COLOR_TYPE_RGB != png_get_color_type(png_ptr, info_ptr))) {
printf("Error: Not 8bit depth or not RGB color");
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
fclose(png_file);
return -1;
}
/* 判断图像和LCD屏那个的分辨率更低 */
if (image_w > width)
min_w = width;
else
min_w = image_w;
if (image_h > height)
min_h = height;
else
min_h = image_h;
valid_bytes = min_w * bpp / 8;
/* 读取解码后的数据 */
fb_line_buf = malloc(valid_bytes);
row_pointers = png_get_rows(png_ptr, info_ptr);//获取数据
unsigned int temp = min_w * 3; //RGB888 一个像素3个bit位
for(i = 0; i < min_h; i++) {
// RGB888转为RGB565
for(j = k = 0; j < temp; j += 3, k++)
fb_line_buf[k] = ((row_pointers[i][j] & 0xF8) << 8) |
((row_pointers[i][j+1] & 0xFC) << 3) |
((row_pointers[i][j+2] & 0xF8) >> 3);
memcpy(screen_base, fb_line_buf, valid_bytes);//将一行数据刷入显存
screen_base += width; //定位到显存下一行
}
/* 结束、销毁/释放内存 */
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
free(fb_line_buf);
fclose(png_file);
return 0;
}
int main(int argc, char *argv[])
{
struct fb_fix_screeninfo fb_fix;
struct fb_var_screeninfo fb_var;
unsigned int screen_size;
int fd;
/* 传参校验 */
if (2 != argc) {
fprintf(stderr, "usage: %s <png_file>\n", argv[0]);
exit(-1);
}
/* 打开framebuffer设备 */
if (0 > (fd = open("/dev/fb0", O_RDWR))) {
perror("open error");
exit(EXIT_FAILURE);
}
/* 获取参数信息 */
ioctl(fd, FBIOGET_VSCREENINFO, &fb_var);
ioctl(fd, FBIOGET_FSCREENINFO, &fb_fix);
line_length = fb_fix.line_length;
bpp = fb_var.bits_per_pixel;
screen_size = line_length * fb_var.yres;
width = fb_var.xres;
height = fb_var.yres;
/* 将显示缓冲区映射到进程地址空间 */
screen_base = mmap(NULL, screen_size, PROT_WRITE, MAP_SHARED, fd, 0);
if (MAP_FAILED == (void *)screen_base) {
perror("mmap error");
close(fd);
exit(EXIT_FAILURE);
}
/* 显示BMP图片 */
memset(screen_base, 0xFF, screen_size);//屏幕刷白
show_png_image(argv[1]);
/* 退出 */
munmap(screen_base, screen_size); //取消映射
close(fd); //关闭文件
exit(EXIT_SUCCESS); //退出进程
}

复制代码