pixel coordinates approved algorithms in C #

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I described the problem a little to help people visualize yourselves.

Put in a picture, the picture has the letters, white background, black text.
Perform image browser to find edge left, right, top, bottom of character BMP files.
The fundamental problem, I do that's alright, but there are some problems:

Problem 1: Speed browse photos.
I can find out and see how the two get-set pixel and lockbit .. is described by the lockbit will browse faster than get-set.
get-set, I make it work, but lockbits is not work.

Who has the solution to this problem does not help me.

Problem 2: the image format
As I said above is only done on the BMP as JPG format,spring term for the browser it is very different.

So, how can convert other formats of BMP is not.

Posted 19-Mar-11 7:30am

nctit09

Updated 23-Mar-11 0:22am

v5

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Albin Abel 19-Mar-11 13:39pm

Would you mind showing your lock bit coding. If we give a generalized answer it may not help to solve your problem.

3 solutions

Solution 2

Here is a code in the article: Unicode Optical Character Recognition
Unicode Optical Character Recognition[^][^]
According author, I have done and detected the top and bottom
1. Image line Identification

public void identify_lines()
{
    int y=image_start_pixel_y;
    int x=image_start_pixel_x;
    bool no_black_pixel;
    int line_number=0;
    line_present=true;
    while(line_present)
    {
        x=image_start_pixel_x;
        while(Convert.ToString (input_image.GetPixel (x,y))==
            "Color [A=255, R=255, G=255, B=255]")
        {
            x++;
            if(x==input_image_width)
            {
                x=image_start_pixel_x;
                y++;
            }
            if(y>=input_image_height)
            {
                line_present=false;
                break;
            }
        }
        if(line_present)
        {
            line_top[line_number]=y;
            no_black_pixel=false;
            while(no_black_pixel==false)
            {
                y++;
                no_black_pixel=true;
                for(x=image_start_pixel_x;x<input_image_width;x++)
                    if((Convert.ToString (input_image.GetPixel (x,y))==
                        "Color [A=255, R=0, G=0, B=0]"))
                no_black_pixel=false;
            }
            line_bottom[line_number]=y-1;
            line_number++;
        }
    }
    number_of_lines=line_number;
}

But now,I want to change this code get-set to lockbit because I think it will be it will be faster. If anyone has any better solutions, please tell me.

Posted 19-Mar-11 16:35pm

nctit09

Comments

nctit09 21-Mar-11 0:26am

help me...hic..:(

Dalek Dave 22-Mar-11 10:00am

Adding code always helps!

Solution 4

You need to use "unsafe" and create an pointer to the pixel. So long as you know the stride, width, and pixel size(your case is 4 bytes) you just add that much to the pointer to get to the location (stride tells you Y wrapping width tells you x location combined with pixel size).

So you could have something like:

C#

unsafe
{
   byte* bPtr;
   for (int y = 0; y < imageData.Length; y++)
   {
      ptr = imageData[y];
      bPtr = (byte*)ptr.ToPointer();
      for (int x = xMin; x <= imageWidth; x+= PixelSize)
      {
          //Do stuff with the pixel bPtr[y * stride + x]
       }
    }
}

Not sure if this is exactly right.. but something along these lines is what you need.

Posted 22-Mar-11 3:18am

N_tro_P

Updated 22-Mar-11 5:36am

v3

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**JF2015** · Accepted Answer · 2011-03-22T03:58:00

When working with bitmaps in C#, you should definitely read Christian Graus' series of articles here on CodeProject. They describe how to access single pixels in a fast way and a lot of other image manipulation technologies. See here:
Image Processing for Dummies with C# and GDI+ Part 1 - Per Pixel Filters[^]
Image Processing for Dummies with C# and GDI+ Part 2 - Convolution Filters[^]
Image Processing for Dummies with C# and GDI+ Part 3 - Edge Detection Filters[^]
Image Processing for Dummies with C# and GDI+ Part 4 - Bilinear Filters and Resizing[^]
Image Processing for Dummies with C# and GDI+ Part 5 - Displacement filters, including swirl[^]
Image Processing for Dummies with C# and GDI+ Part 6 - The HSL color space[^]