Simple reading in a file help needed.

This is a discussion on Simple reading in a file help needed. within the C Programming forums, part of the General Programming Boards category; So im just trying to read in an pgm file and store it in an array, Code: int** imageArray; //allocate ...

  1. #1
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    Simple reading in a file help needed.

    So im just trying to read in an pgm file and store it in an array,

    Code:
    int** imageArray;
    
    
    //allocate the image array
    	imageArray = (int**) malloc(row * sizeof(int*));
    	for(i = 0; i < row; i++)
    		imageArray[i] = (int*) malloc(col * sizeof(int));
    		
    	for(i=0; i < row; i++)
    	{
    
    
    		for(j=0; j < col; j++)
    		{
    			fscanf(fpI, "%d ", &imageArray[i][j]);
    		}
    	}
    It stores about 1/3 of the file into the array, and then starts printing 6815940 6819608 followed by a bunch of 0's.
    Thanks for any help in advance.

  2. #2
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    You have problems printing the array elements so what's the code for it?
    Also show us the header of the pgm file.

    BTW: Don't cast the return value of malloc in C.

    Bye, Andreas

  3. #3
    and the hat of wrongness Salem's Avatar
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    And what is the format of the image file?
    Post a couple of rows.

    Code:
        for(i=0; i < row && !feof(fpl); i++)
        {
            for(j=0; j < col && !feof(fpl); j++)
            {
                if ( fscanf(fpI, "%d ", &imageArray[i][j]) != 1 ) {
                    fprintf(stderr,"Problem at row %d col %d\n", i, j );
                }
            }
        }
    Also, add some diagnostic and error checking to your code.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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    the pgm files format is as follows
    Code:
    P2
    # Image generated by Artifex Ghostscript (device=pgm)
    448 336
    255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
    and my printing to the file is as follows
    Code:
    //writing to the new file
    		//header
    	fprintf(fpO, "%s%s%d %d\n%s", InFileType, InFileDescription, row, col, maxValueIn);
    		//Binary threshold
    		if(Uinput == 1)
    		{
    		for(i = 0; i < row; i++)
    		{
    			for(j = 0; j < col; j++)
    			{
    				fprintf(fpO,"%d ", imageArray[i][j]);
    			}
    			fprintf(fpO,"\n");
    		}
    		}//end Binary threshold
    thanks for any input.

  5. #5
    and the hat of wrongness Salem's Avatar
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    All I can suggest is add debug prints (or use a debugger) and step through the code.
    There isn't anything obviously wrong with what you've posted so far.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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    Quote Originally Posted by Salem View Post
    All I can suggest is add debug prints (or use a debugger) and step through the code.
    There isn't anything obviously wrong with what you've posted so far.
    do you have any suggestions for debuggers? and would using fgets to get all the header info effect my fscanf i use to declare the array?

    Code:
    //declare variables for image file intake
    	int** imageArray;
    	char InFileType [10];
    	char InFileDescription [100];
    	char rowRead;
    	char inDimensions [10];
    	char maxValueIn [10];
    	char fileDescription [100];
    	unsigned int row, col, i, j, maxValue;
    
    
    	//reading in the information
    	fgets(InFileType, 10, fpI);
    	fgets(InFileDescription, 100, fpI);
    	fgets(inDimensions, 10, fpI);
    	row = atoi(strtok(inDimensions, " "));
    	col = atoi(strtok(NULL, " "));
    	fgets(maxValueIn, 10, fpI);
    	maxValue = atoi(maxValueIn);

  7. #7
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    Quote Originally Posted by Denis St. John View Post
    do you have any suggestions for debuggers? and would using fgets to get all the header info effect my fscanf i use to declare the array?

    Code:
    //declare variables for image file intake
        int** imageArray;
        char InFileType [10];
        char InFileDescription [100];
        char rowRead;
        char inDimensions [10];
        char maxValueIn [10];
        char fileDescription [100];
        unsigned int row, col, i, j, maxValue;
    
    
        //reading in the information
        fgets(InFileType, 10, fpI);
        fgets(InFileDescription, 100, fpI);
        fgets(inDimensions, 10, fpI);
        row = atoi(strtok(inDimensions, " "));
        col = atoi(strtok(NULL, " "));
        fgets(maxValueIn, 10, fpI);
        maxValue = atoi(maxValueIn);
    I ran a debugg on the Fscanf, and its returning 0 when the array is at i = 150 and j =297 when rows = 448 and col = 336.

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    Idk if anyone still have some info, but im trying to eliminate fscanf.
    Code:
    	//allocate the image array
    	imageArray = malloc(row * sizeof(int*));
    	for(i = 0; i < row; i++)
    		imageArray[i] = malloc(col * sizeof(int));
    
    
    	for(i=0; i < row; i++)
    	{
    		for(j=0; j < (col/16); j++)
    		{
    			fgets(rowRead, 10000, fpI);
    			for(k=0; k< 16; k++)
    			{
    				sscanf(rowRead, "%d", &imageArray[i][(j*16)+k]);
    			}
    		}
    	}
    it's storing the image kind of blocky. any thoughts?

  9. #9
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    Is your image data int sized? Unsigned char is what I've seen in some image formats.

    When you look at the data with a hex editor, can you get a better description than "blocky", of the problem?

    There are freeware hex editors at the file depot sites, for Windows.
    Last edited by Adak; 02-28-2013 at 08:08 PM.

  10. #10
    and the hat of wrongness Salem's Avatar
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    At this point, I would suggest post a whole program.

    > it's storing the image kind of blocky. any thoughts?
    Because sscanf doesn't work it's way through a string in the same way that fscanf works it's way through a file stream.

    But since you decided to ignore previous suggestions like adding lots of error checking, but instead go off and try some other half-assed approach, I'll just leave it at that.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  11. #11
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    Try creating a few trivial images, eg 1 pixel, 7 x 8, and so on.

    |Most likely the problem is that you haven't got row and col correct, or the image itself is defective.
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