Question

I have a simple file that reads in a monochrome bitmap (i.e. black and white) and prints out x’s to represent the black portion. However, I noticed that for some reason I need to add the code

img.RotateFlip(RotateFlipType.Rotate270FlipY);

for it to show up “normally.” In other words, it seems that something in either my code or the implementation of the built-in functions is rotating and flipping the image as it’s read in, acting counter to what I intend.

I’m betting on this is a silly mistake more than “working as intended,” so I’m including the relevant code below:

    private void button1_Click(object sender, EventArgs e)
    {
        if (openFileDialog1.ShowDialog() == DialogResult.OK)
        {
            // Stream objects for capturing image data
            StreamReader sr = new StreamReader(openFileDialog1.OpenFile());
            MemoryStream memStream = new MemoryStream();

            // Image objects containing image data
            Bitmap img = (Bitmap) Bitmap.FromStream(sr.BaseStream);


            /**** HACK ****/
            //img.RotateFlip(RotateFlipType.Rotate270FlipY);
            /****      ****/


            // Save the image data to our memory stream
            img.Save(memStream, ImageFormat.Gif);

            // Save data to a byte array
            byte[] imgData = memStream.ToArray();

            // Print image data
            for (int x = 0; x < img.Width; ++x)
            {
                Color rgb = new Color();
                for (int y = 0; y < img.Height; ++y)
                {
                    rgb = img.GetPixel(x, y);

                    if (rgb.ToArgb().Equals(Color.White.ToArgb()))
                    {
                       textBox1.AppendText(" ");
                    }
                    else
                    {
                        textBox1.AppendText("x");
                    }
                }
                textBox1.AppendText(Environment.NewLine);
            }
        }
    }

I read in a bitmap of the letter ‘B’ and it gives me the following.

Without the “hack”:

     x                         x        
     x                         x        
     x                         x        
     xx                       xx        
     xxxxxxxxxxxxxxxxxxxxxxxxxxx        
     xxxxxxxxxxxxxxxxxxxxxxxxxxx        
     xxxxxxxxxxxxxxxxxxxxxxxxxxx        
     x            x            x        
     x            x            x        
     x            x            x        
     x            x            x        
     x            x            x        
     x            x            x        
     x            x            x        
     x            x            x        
                  x            x        
      x          xx                     
      x         xxxx          x         
      xx       xxx x          x         
       xx     xxxx xx        xx         
       xxxxxxxxxx   xxx    xxx          
         xxxxxxx    xxxxxxxxxx          
           xxx       xxxxxxx            
                       xxx              

With the “hack”:

     xxxxxxxxxxxxxxx                   
        xxxx         xxx               
         xxx           xxx             
         xxx            xx             
         xxx             xx            
         xxx             xx            
         xxx             xxx           
         xxx             xxx           
         xxx             xxx           
         xxx            xxx            
         xxx           xxxx            
         xxx          xxxx             
         xxx         xxxx              
         xxxxxxxxxxxxxx                
         xxx          xxx              
         xxx            xxx            
         xxx             xxx           
         xxx             xxx           
         xxx              xxx          
         xxx              xxx          
         xxx              xxx          
         xxx              xx           
         xxx             xxx           
         xxx             xx            
         xxx            xxx            
        xxxx          xxx              
     xxxxxxxxxxxxxxxx                  

I very much look forward to having my mistake pointed out to me. 🙂

Thanks in advance!

Answer 1

Your problem is that you’re building rows with your inner loop to put into the text box, but your inner loop loops over y. Try changing the nesting of those loops, and see what you get. Also, your y loop needs to start at the top, or the image will be upside down.

    for (int y = img.Height - 1; y >= 0; --y)
    {
        Color rgb = new Color();
        for (int x = 0; x < img.Width; ++x)
        {
            rgb = img.GetPixel(x, y);

            if (rgb.ToArgb().Equals(Color.White.ToArgb()))
            {
               textBox1.AppendText(" ");
            }
            else
            {
                textBox1.AppendText("x");
            }
        }
        textBox1.AppendText(Environment.NewLine);
    }