sd_jpeg代码分享

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sd_jpeg代码分享

上周在帮客户调试sd_jpeg工程代码的过程中，在原工程基础上增加了libjpeg的图片压缩函数，实现从SD卡读取jpg图片并将图像元数据另外存储成jpg图片后，再通过LCD屏显示，其中图片压缩函数代码如下所示。

1. /*!
   
2. * @brief  Jpeg compress
   
3. * @param  file:    pointer to the jpg raw data
   
4. * e
   
5. */
   
6. status_t JpegCompress(uint8_t* buffer)
   
7. {
   
8.     struct jpeg_compress_struct cinfo;
   
9.     struct jpeg_error_mgr jerr;
   
10.     uint8_t* scanlines = buffer;
    
11.     JSAMPROW row_pointer;
    
12.     uint32_t row_stride     = 0;   /* physical row width in image buffer */
    
13.     FRESULT error;
    
14. 
    
15.     FILE fJpeg;
    
16.     char JpegFilename[20];
    
17.     static uint32_t JpegFilenameIndex = 0u;
    
18. 
    
19.     PRINTF("Start of JPEG Compression... ");
    
20. 
    
21.     if(JpegFilenameIndex > 9999u)
    
22.     {
    
23.         JpegFilenameIndex = 0u;
    
24.     }
    
25. 
    
26.     sprintf(JpegFilename, "/IMG_%04d.jpg", ++JpegFilenameIndex);
    
27. 
    
28.     error = f_open(&fJpeg, _T(JpegFilename), (FA_WRITE | FA_CREATE_ALWAYS));
    
29.     if (error)
    
30.     {
    
31.         if (error == FR_EXIST)
    
32.         {
    
33.             PRINTF("File exists.\r\n");
    
34.         }
    
35.         else
    
36.         {
    
37.             PRINTF("Open file failed.\r\n");
    
38.             return -1;
    
39.         }
    
40.     }
    
41. 
    
42.     /* Initialize the JPEG compression object with default error handling. */
    
43.     cinfo.err = jpeg_std_error(&jerr);
    
44.     jpeg_create_compress(&cinfo);
    
45. 
    
46.     /* Initialize JPEG parameters.*/
    
47.     cinfo.in_color_space = JCS_RGB; /* arbitrary guess */
    
48.     jpeg_set_defaults(&cinfo);
    
49. 
    
50.     /* Specify the source format. */
    
51.     cinfo.in_color_space = JCS_RGB;
    
52.     cinfo.input_components = 3u;
    
53.     cinfo.data_precision = 8u;
    
54.     cinfo.image_width = (JDIMENSION)APP_FB_WIDTH;
    
55.     cinfo.image_height = (JDIMENSION)APP_FB_HEIGHT;
    
56. 
    
57.     /* Now that we know input colorspace, fix colorspace-dependent defaults */
    
58.     jpeg_default_colorspace(&cinfo);
    
59. 
    
60.     /* Specify data destination for compression */
    
61.     jpeg_stdio_dest(&cinfo, &fJpeg);
    
62. 
    
63.     jpeg_set_quality(&cinfo, 100u, true);
    
64. 
    
65.     /* Start compressor */
    
66.     jpeg_start_compress(&cinfo, TRUE);
    
67.     row_stride = APP_FB_STRIDE_BYTE;
    
68.     /* Process data */
    
69.     while (cinfo.next_scanline < cinfo.image_height)
    
70.     {
    
71.         row_pointer = (JSAMPROW)(scanlines+cinfo.next_scanline * row_stride);
    
72.         jpeg_write_scanlines(&cinfo, &row_pointer, COMPRESS_LINES);
    
73.     }
    
74. 
    
75.     /* Finish compression and release memory */
    
76.     jpeg_finish_compress(&cinfo);
    
77.     jpeg_destroy_compress(&cinfo);
    
78. 
    
79.     f_close(&fJpeg);
    
80. 
    
81.     PRINTF("Done: %s is saved. \r\n", JpegFilename);
    
82. 
    
83.     return kStatus_Success;
    
84. }

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evkbimxrt1050_sd_jpeg.zip (2.45 MB, 下载次数: 3)

2021-8-16 17:54 上传

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