[Libjpeg-devel-6x] Jpeg decompress problem

[Reka S. <rek...@gm...>]

Hi All,

I am very new for libjpeg and mailing list also.

I am trying to decompress jpg image using following code.
Input parameters are image name, width and height.
return type is custom structure called IMG_MATRIX.

typedef struct img_matrix{
    int x;
    int y;
    int intensity_r;
    int intensity_g;
    int intensity_b;
} IMG_MATRIX;

I need to get pixel values (R,G,B) and create new jpeg image.

Issue is i got blurred image when I try generate new new jpeg image. (see
attachments)
I think issue is having my decompress code. because I can generate correct
image if I read image using OpenCv.
If anyone can help to solve this issue It would be grate.

Best Regards,

*my code of read jpeg as follows. *

IMG_MATRIX *katussa_read_jpeg(char *watermarked_image_name, int width, int
height)
{
    // Using this uninitialized pointer later to store raw, uncompressd
image
    unsigned char *raw_image = NULL;
    char *filename = watermarked_image_name;

    // Dimensions of the image we want to write
    //int width = 512;
    //int height = 512;
    int bytes_per_pixel = 3; /* or 1 for GRACYSCALE images */
    int color_space = JCS_RGB; /* or JCS_GRAYSCALE for grayscale images */

    int index = width*height*41;
    IMG_MATRIX *img_matrix = NULL;
  img_matrix = (IMG_MATRIX*) malloc(index);

    // variables for cordinates of img_matrix

    int x, y;
    int total_pixel = width*height;

    // These are standard libjpeg structures for reading(decompression)
    struct jpeg_decompress_struct cinfo;
    struct jpeg_error_mgr jerr;

    // libjpeg data structure for storing one row, that is, scanline of an
image
    JSAMPROW row_pointer[1];

    FILE *infile = fopen( filename, "rb" );
    unsigned long *location;
    int i = 0;

    if ( !infile )
    {
        printf("Error opening jpeg file %s\n!", filename );
        exit;
    }

    // Here we set up the standard libjpeg error handler
    cinfo.err = jpeg_std_error( &jerr );

    // Setup decompression process and source, then read JPEG header
    jpeg_create_decompress( &cinfo );

    // This makes the library read from infile
    jpeg_stdio_src( &cinfo, infile );

    // Reading the image header which contains image information
    jpeg_read_header( &cinfo, TRUE );

    // Start decompression jpeg here
    jpeg_start_decompress( &cinfo );

    // Allocate memory to hold the uncompressed image
    raw_image = (unsigned char*)malloc(
cinfo.output_width*cinfo.output_height*cinfo.num_components );

    // Now actually read the jpeg into the raw buffer
    row_pointer[0] = (unsigned char *)malloc(
cinfo.output_width*cinfo.num_components );

    location = (unsigned long*)malloc(
cinfo.output_width*cinfo.output_height*cinfo.num_components );

    // Read one scan line at a time
    long long int pixel_index = -1;
    y = 0;
    unsigned long count = 0;
    while( cinfo.output_scanline < cinfo.image_height )
    {

        jpeg_read_scanlines( &cinfo, row_pointer, 1 );
        x = 0;
        for( i=0; i<cinfo.image_width*cinfo.num_components; i++){
            location[count] = row_pointer[0][i];

            if((count%3)==0)
            {
                pixel_index++;
                img_matrix[pixel_index].x = x;
                img_matrix[pixel_index].y = y;
                img_matrix[pixel_index].intensity_r = row_pointer[0][i];

                x++;
            }
            if((count%3)==1)
            {
                img_matrix[pixel_index].intensity_g =  row_pointer[0][i];
            }
            if((count%3)==2)
            {
                img_matrix[pixel_index].intensity_b =  row_pointer[0][i];
            }

            count++;

        }
        y++;
        //break;

    }

    // Wrap up decompression, destroy objects, free pointers and close open
files
    jpeg_finish_decompress( &cinfo );
    jpeg_destroy_decompress( &cinfo );
    free( row_pointer[0] );
    fclose( infile );

    return img_matrix;
}

-- 
Reka Sandaruwan
Senior Engineer
WSO2