Image Median Filtering (Selection Algorithm)

[Deathfish]

Homework Statement

I started working on a C++ image median filter for fun... I'm supposed to read a 30x30 16-bit grayscale binary image and apply selection algorithm. 3x3 kernel.

Please help output is messed up and i don't know where to start fixing it.

Homework Equations

using stdio.h

For every pixel aside from edges,
- 3x3 neighbourhood is assigned pixel numbers 1-9 by relative position.
- Scanning left to right then next row.
- If there is a smaller number than current number then number is replaced.
- Repeat for rest of neighbourhood.
- ((9-1)/2 + 1)th value is median
- continue for next pixel

The Attempt at a Solution

- headers, definitions left out

void main()
{
unsigned short matrix[30][30];
unsigned short filtered[30][30];

int kernel[9];
int ordered[9];
int y, x;
int minvalue;
int i, j;
int count, jcount;
int medcount;
int median, upper, lower;

FILE *original;
FILE *output;

if ((original = fopen ("F:\\test\\ArrayQ.bin", "rb")) == NULL)
{
printf("Error opening binary file");
}

if (fread(matrix, sizeof(unsigned short), 900, original) != 900)
{
printf("Error reading binary file");
}

fclose(original);

for (y=1;y<29;y++)
{
for (x=1;x<29;x++)
{
kernel[1]=matrix[y-1][x-1];
kernel[2]=matrix[y-1][x];
kernel[3]=matrix[y-1][x+1];
kernel[4]=matrix[y][x-1];
kernel[5]=matrix[y][x];
kernel[6]=matrix[y][x+1];
kernel[7]=matrix[y+1][x-1];
kernel[8]=matrix[y+1][x];
kernel[9]=matrix[y+1][x+1];

for (count=0;count<SIZE;count++)
{
i=kernel[count];
minvalue=i;
jcount=count+1;

while(jcount<SIZE)
{
j=kernel[jcount]
if (j < minvalue)
{
minvalue=j;
}
jcount++;
}

ordered[count]=minvalue;
}

if (SIZE%2==1)
{
medcount=((SIZE-1)/2)+1;
median=ordered[medcount];
}
else
{
lower=SIZE/2;
upper=(SIZE/2)+1;
median=(ordered[lower]+ordered[upper])/2;
}

printf("%d\t", median);
}
}

if ((output = fopen ("F:\\test\\avefilter.bin", "wb")) == NULL)
{
printf("\nError creating binary file!\n\n");
}
if (fwrite (filtered, sizeof (unsigned short), 900, output) !=900)
{
printf("\nError writing binary file!\n\n");
}

fclose(output);

}

 

[KataKoniK]

Hello! It looks like you have a good start on your C++ image median filter program. Can you provide more information on what specifically is going wrong with the output? Are the values incorrect or is the image distorted? It would also be helpful to see your code so we can better understand the issue and provide guidance on how to fix it.