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POError reading .jpeg file using libjpeg
 

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  1. POError reading .jpeg file using libjpeg
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    <p>I am getting NULL pointer exception in the function <code>jpeg_read_header()</code> in following code while the input image file is successfully read by FILE object.</p> <pre><code>#include "jpeglib.h" #include &lt;iostream&gt; using namespace std; void decode_frame(char *filename) { unsigned char* raw_image; JSAMPROW row_pointer[1]; unsigned long location = 0; struct jpeg_error_mgr jerr; struct jpeg_decompress_struct cinfo ; FILE *infile = fopen(filename, "rb" ); if (infile == NULL ) { printf("Error opening jpeg file %s\n!", filename ); return -1; } cinfo.err = jpeg_std_error(&amp;jerr); /* create decompressor */ jpeg_create_decompress(&amp;cinfo); /* this makes the library read from infile */ jpeg_stdio_src(&amp;cinfo, infile ); /* read jpeg header */ jpeg_read_header(&amp;cinfo, TRUE); /* decompress */ jpeg_start_decompress(&amp;cinfo); /*allocate memory */ 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 ); /* read scanlines */ while (cinfo.output_scanline &lt; cinfo.output_height) { jpeg_read_scanlines( &amp;cinfo, row_pointer, 1 ); for( int i=0; i &lt; cinfo.image_width*cinfo.num_components;i++) raw_image[location++] = row_pointer[0][i]; } /* clean up */ jpeg_finish_decompress(&amp;cinfo); jpeg_destroy_decompress(&amp;cinfo); fclose( infile ); free( row_pointer[0] ); } int main(){ char *f = "Example.jpg"; decode_frame(f); return 0; } </code></pre> <p>The value of cinfo alfter <code>jpeg_stdio_src(&amp;cinfo, infile )</code> function call is :</p> <pre><code>cinfo{err=0x0020f8fc mem=0x021cb320 progress=0x00000000 ...} progress 0x00000000 {progress_monitor=??? pass_counter=??? pass_limit=??? ...} client_data 0xcccccccc void * is_decompressor 1 global_state 200 src 0x021c4480 {next_input_byte=0x00000000 &lt;Bad Ptr&gt; bytes_in_buffer=0 init_source=0x686ccb50 ...} image_width 0 image_height 0 num_components 0 jpeg_color_space JCS_UNKNOWN out_color_space JCS_UNKNOWN scale_num 0 scale_denom 0 output_gamma 0.00000000000000000 buffered_image 0 raw_data_out 0 dct_method JDCT_ISLOW </code></pre> <p>Where I am getting wrong? This is the first time I am using image library.</p>
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