jpeg2rle发布

最新推荐文章于 2022-01-06 16:19:28 发布

最新推荐文章于 2022-01-06 16:19:28 发布 · 89 阅读

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#移动开发 #嵌入式

本文介绍了一个名为jpeg2rle的小工具，该工具能够将JPEG格式的图片转换为RLE压缩格式，适用于嵌入式设备的启动LOGO。文中详细展示了如何通过解压JPEG文件并采用RLE算法进行编码的具体实现。

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文章出处：http://www.limodev.cn/blog
作者联系方式：李先静 <xianjimli at hotmail dot com>

jpeg2rle发布

RLE(run-length encoding)是一个压缩算法，它最大的好处就是解压速度快。用来做嵌入式设备开机时的LOGO是不错的选择，android里也使用了这种格式。今天写了个小工具jpeg2rle，它把JPEG文件转换成RLE文件。

o 把一行数据写入RLE文件。

void
put_scanline_to_file (FILE * outfile, char *scanline, int width,
int row_stride)
{
int i = 0;
char *pixels = scanline;
char *start = scanline;

while (i < width)
{
unsigned short n = 0;
for (; i < width; i++, n++)
{
if (memcmp (pixels, pixels + 3 * n, 3) != 0)
{
break;
}
}
unsigned char r = pixels[0];
unsigned char g = pixels[1];
unsigned char b = pixels[2];
unsigned short rle565 = ((r >> 3) << 11) | ((g >> 2) << 5) | (b >> 3);

fwrite (&n, 2, 1, outfile);
fwrite (&rle565, 2, 1, outfile);
pixels += 3 * n;
}

return;
}

o 解压jpeg

int jpeg2rle (char *filename, char *outfilename)
{
struct jpeg_decompress_struct cinfo;
int i = 0;
struct my_error_mgr jerr;
FILE *infile;
FILE *outfile;
JSAMPARRAY buffer;
int row_stride;

if ((infile = fopen (filename, "rb")) == NULL)
{
fprintf (stderr, "can't open %s/n", filename);
return 0;
}

if ((outfile = fopen (outfilename, "wb")) == NULL)
{
fprintf (stderr, "can't open %s/n", outfilename);
fclose (infile);
return 0;
}

cinfo.err = jpeg_std_error (&jerr.pub);
jerr.pub.error_exit = my_error_exit;

if (setjmp (jerr.setjmp_buffer))
{
jpeg_destroy_decompress (&cinfo);
fclose (infile);
fclose (outfile);
return 0;
}
jpeg_create_decompress (&cinfo);
jpeg_stdio_src (&cinfo, infile);

(void) jpeg_read_header (&cinfo, TRUE);
(void) jpeg_start_decompress (&cinfo);
row_stride = cinfo.output_width * cinfo.output_components;
buffer = (*cinfo.mem->alloc_sarray)
((j_common_ptr) & cinfo, JPOOL_IMAGE, row_stride, 1);
printf("size: %dx%d/n", cinfo.output_width, cinfo.output_height);
while (cinfo.output_scanline < cinfo.output_height)
{
(void) jpeg_read_scanlines (&cinfo, buffer, 1);
put_scanline_to_file (outfile, buffer[0], cinfo.output_width,
row_stride);
}

(void) jpeg_finish_decompress (&cinfo);
jpeg_destroy_decompress (&cinfo);

fclose (infile);
fclose (outfile);

return 1;
}

o 主函数

int main (int argc, char *argv[])
{
if (argc != 3)
{
printf ("usage: %s jpeg rle/n", argv[0]);
}
else
{
jpeg2rle(argv[1], argv[2]);
}

return 0;
}

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