Finding an smaller image from a larger image (help please)

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Hello can anyone help me please, i cannot seem to figure out why this code can't find the image i'm looking for if they are located on more than 50% of my screen and works perfectly and locate perfect if the image is on the left 50% of my screen. :/

C#

private int[,] isImageThere(Bitmap fullImage, Bitmap smallImage)
{
    Color[,] fullPixels = ImageToArray(fullImage);
    Color[,] smallPixels = ImageToArray(smallImage);
    int R = 0;
    int G = 0;
    int B = 0;
    try
    {
        // Iterate through every row
        for (int fullColumn = 0; fullColumn < fullImage.Width; fullColumn++)
        {
            //1200 error
            if (fullColumn >= fullImage.Width)
                break;
            // Iterate through every pixel in the row
            for (int fullRow = 0; fullRow < fullImage.Height; fullRow++)
            {
                if (fullRow >= fullImage.Height)
                    break;
                // If the current pixel on the full image is the
                // same as the top left pixel on the small image...
                if (/*(fullPixels[fullRow, fullColumn] == smallPixels[0, 0])*/
                    (Convert.ToInt16(fullPixels[fullColumn, fullRow].R) + Convert.ToInt16(fullPixels[fullColumn, fullRow].G) + Convert.ToInt16(fullPixels[fullColumn, fullRow].B) - (Convert.ToInt16(smallPixels[0, 0].R) + Convert.ToInt16(smallPixels[0, 0].G) + Convert.ToInt16(smallPixels[0, 0].B))) >= -2 &&
                    (Convert.ToInt16(fullPixels[fullColumn, fullRow].R) + Convert.ToInt16(fullPixels[fullColumn, fullRow].G) + Convert.ToInt16(fullPixels[fullColumn, fullRow].B) - (Convert.ToInt16(smallPixels[0, 0].R) + Convert.ToInt16(smallPixels[0, 0].G) + Convert.ToInt16(smallPixels[0, 0].B))) <= 2
                    )
                {
                    // So far, we haven't found a mismatched pixel
                    bool badPixel = false;
                    try
                    {
                        // Iterate through every row in the small image
                        for (int smallRow = 0; smallRow < smallImage.Width; smallRow++)
                        {
                            // Iterate through every pixel in the row
                            for (int smallColumn = 0; smallColumn < smallImage.Height; smallColumn++)
                            {
                                // If the pixel on the full image isn't the same as on the small image...
                                R = (fullPixels[fullColumn + smallColumn, fullRow + smallRow].R - smallPixels[smallColumn, smallRow].R);
                                G = (fullPixels[fullColumn + smallColumn, fullRow + smallRow].G - smallPixels[smallColumn, smallRow].G);
                                B = (fullPixels[fullColumn + smallColumn, fullRow + smallRow].B - smallPixels[smallColumn, smallRow].B);
                                if (R < 0)
                                    R = R * -1;
                                if (G < 0)
                                    G = G * -1;
                                if (B < 0)
                                    B = B * -1;
                                //if (fullPixels[fullColumn + smallColumn, fullRow + smallRow] != smallPixels[smallColumn, smallRow])
                                if (
                                    (R >= 2) &&
                                    (G >= 2) &&
                                    (B >= 2)
                                   )
                                {
                                    // There is a mismatched pixel so set bad pixel to true
                                    badPixel = true;
                                    break;
                                }
                                else
                                    badPixel = false;
                                R = 0;
                                G = 0;
                                B = 0;
                            }
                            // If we found a bad pixel, break out of outer loop
                            if (badPixel == true)
                            {
                                break;
                            }
                        }
                    }
                    catch { }
                    // If we passed through all pixels in small image, return location
                    if (badPixel == false)
                    {
                        int[,] res = new int[,] { { fullColumn, fullRow } };
                        return res;
                    }
                }
            }
        }
    }
    catch { }
    // If we looped until here, not match was found
    return null;
}

Posted 11-Feb-11 15:14pm

Member 4352789

Updated 11-Feb-11 15:15pm

v2

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Comments

Sergey Alexandrovich Kryukov 11-Feb-11 21:21pm

No explanation. How it supposed to work, what you want to achieve?

2 solutions

Solution 2

You can use this method for re size image

public Bitmap ReSizeBitmap(Bitmap btp, int width, int height)
        {
            int originalW = btp.Width;
            int originalH = btp.Height;

            Bitmap bmp = new Bitmap(width, height);
            //create a new graphic from the Bitmap
            Graphics graphic = Graphics.FromImage((Image)bmp);
            graphic.InterpolationMode = InterpolationMode.HighQualityBicubic;
            //draw the newly resized image
            graphic.DrawImage(btp as Image, 0, 0, width, height);
            graphic.Dispose();
            //return the image
            return bmp;
        }

Posted 11-Feb-11 16:40pm

shakil0304003

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tgis.top · Accepted Answer · 2011-02-11T16:36:00

The two line below will raise a IndexOutOfException.

SQL

//1200 error
 if (fullColumn >= fullImage.Width)
     break;

C#

if (fullRow >= fullImage.Height)
                    break;

It should be like this；

C#

if (fullColumn >= fullImage.Width-smallImage.Width)
                break;

your algorithm is very very slow. Every Image has some key point(also corner point), that is, the highest color change ratio point. So you can use same algorithm extract the corner-point-constellation than match the constellation.