For loop ends prematurely

Question

I've created a program that processes images in c#. For some reason, I've made pretty much the most simple double for loop possible, and it refuses to work. This loop ends at x=78 and y=78, reliably every time. I've been looking at this forever, and I can not figure it out! Code:

try 
{
     for (int y = 0; y < inputHeight; y++)
     {
         for (int x = 0; x < inputWidth; x++)
         {
             if (x == 0 && y == 0)
                 continue;
             int xpix = x;
             int ypix = y;
             Color color = inputImage.GetPixel(xpix, ypix);
             colorBucket[counter] = color.R;
             if (counter < byteSize - 1)
                 colorBucket[counter + 1] = color.G;
             if (counter < byteSize - 2)
                 colorBucket[counter + 2] = color.B;
             counter += 3;        
         }
    }
}
catch (Exception e)
{
    System.Diagnostics.Debugger.Log(1, "Error", e.ToString());
}

Visual studio specifically tells me that both conditions are true, regardless of the fact that the loop has exited, and they are also true when looping. The size of colorBucket is huge, and the loop exits when count is about a third of the size of colorBucket through itself. Along with that, no exceptions are thrown, and the debug point I have set in my catch statement is never called.

EDIT: the width and height of the image are 844 pixels, also, the loop still appears to fail once the inner code is removed.

EDIT 2: So I've figured out something pretty important, the loop doesn't actually end prematurely, but somehow, counter is not equal to the number of colors in the colorbucket.

You're probably getting an exception during the loop. Wrap the loop in a `try/catch` block and see what happens. — Dai, Dec 15 '13 at 03:58
Use breakpoints and check the inputHeight and inputWidth variable when it hits your first for loop. That will tell you if the loops are really ending prematurely or set to 78x78 as @dasblinkenlight mentioned — BRogers, Dec 15 '13 at 04:02
both conditions in the for loops are true when I put a breakpoint after the loop. inputHeight is NOT 78, neither is inputWidth, I stepped through the loop approximatley 20 times. Also, visual studios tells me that even though we've left the loops, the conditions are still true. — Dylan Katz, Dec 15 '13 at 04:05
There's no way to see if the conditions are true **after** the loop, because loop variables are out of scope by then. — Sergey Kalinichenko, Dec 15 '13 at 04:07
@dasblinkenlight odd, when I mouse over the condition, it says "true" Also, I can view the values of x and y after the loop is over. — Dylan Katz, Dec 15 '13 at 04:08
When you step through it... what is the value of `inputHeight` and `inputWidth`? hover over them when it hits the for loop... — BRogers, Dec 15 '13 at 04:15
@dasblinkenlight oops, forgot the brace, but yes i did remove some code, though I ran the code in the post with the same results. No exceptions are thrown. — Dylan Katz, Dec 15 '13 at 04:42

Sergey Kalinichenko · Answer 1 · 2013-12-15T04:09:37.200

3

It appears that your inputHeight and inputWidth are defined incorrectly. Try changing the loop headers to use the properties of your inputImage, like this:

for (int y = 0; y < inputImage.Height; y++)
{
    for (int x = 0; x < inputImage.Width; x++)
    {
        ...
    }
}

Another problem is the size of your colorBucket array: your loops cannot run more than one third its size, combined. For example, if the size of the colorBucket array is 18252, your loop will run exactly 78x78 times before throwing an exception.

edited Dec 15 '13 at 04:09

answered Dec 15 '13 at 04:02

Sergey Kalinichenko

714,442
84
1,110
1,523

inputHeight and inputWidth are exactly what I expect them to be upon inspection in debug mode. – Dylan Katz Dec 15 '13 at 04:03
@DylanKatz Are they equal to `inputImage.Height` and `inputImage.Width`? – Sergey Kalinichenko Dec 15 '13 at 04:04
@DylanKatz what are the values? – BRogers Dec 15 '13 at 04:16
844 for width, same for height. – Dylan Katz Dec 15 '13 at 04:18

score 0 · Accepted Answer · answered Dec 15 '13 at 06:42

0

Well, it turns out that It had to do with the fact that I was multiplying the size of colorBucket in to thirds outside of this code. I understand if you find in necessary to close this question, as it's quite specific to this situation.

answered Dec 15 '13 at 06:42

Dylan Katz

194
2
14

For loop ends prematurely

2 Answers2