cario库能显示jpeg图像吗
时间: 2023-12-10 13:37:19 浏览: 27
是的,Cairo库可以显示JPEG图像。要在Cairo中加载和显示JPEG图像,需要使用libjpeg库。以下是一个使用Cairo和libjpeg的示例代码,可以读取JPEG图像并将其绘制到Cairo的绘图上下文中:
```c
#include <cairo.h>
#include <jpeglib.h>
void draw_jpeg(cairo_t *cr, const char *filename) {
struct jpeg_decompress_struct cinfo;
struct jpeg_error_mgr jerr;
JSAMPROW row_pointer[1];
FILE *infile = fopen(filename, "rb");
if (!infile) {
fprintf(stderr, "Error opening JPEG file %s\n", filename);
return;
}
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_decompress(&cinfo);
jpeg_stdio_src(&cinfo, infile);
jpeg_read_header(&cinfo, TRUE);
jpeg_start_decompress(&cinfo);
int row_stride = cinfo.output_width * cinfo.output_components;
unsigned char *buffer = (unsigned char *)malloc(row_stride);
while (cinfo.output_scanline < cinfo.output_height) {
row_pointer[0] = buffer;
jpeg_read_scanlines(&cinfo, row_pointer, 1);
for (int i = 0; i < row_stride; i += cinfo.output_components) {
unsigned char r = buffer[i];
unsigned char g = buffer[i + 1];
unsigned char b = buffer[i + 2];
cairo_set_source_rgb(cr, r / 255.0, g / 255.0, b / 255.0);
cairo_rectangle(cr, i / cinfo.output_components, cinfo.output_scanline - 1, 1, 1);
cairo_fill(cr);
}
}
free(buffer);
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
fclose(infile);
}
int main(int argc, char **argv) {
cairo_surface_t *surface = cairo_image_surface_create(CAIRO_FORMAT_RGB24, 640, 480);
cairo_t *cr = cairo_create(surface);
draw_jpeg(cr, "example.jpg");
cairo_surface_write_to_png(surface, "output.png");
cairo_destroy(cr);
cairo_surface_destroy(surface);
return 0;
}
```
这个示例代码使用libjpeg库读取JPEG图像,然后将像素值转换为Cairo的RGB颜色,最后将每个像素绘制到Cairo的绘图上下文中。