Get all pixel information of an image efficiently

Question

I made a program to get all image pixel RGB color codes from picture. Basically, it sets y position on constant and changes x position zero to width and also y by looping. <

Answer 1

Take a look at this:

var data = mypic.LockBits(
    new Rectangle(Point.Empty, mypic.Size),
    ImageLockMode.ReadWrite, mypic.PixelFormat);
var pixelSize = data.PixelFormat == PixelFormat.Format32bppArgb ? 4 : 3; // only works with 32 or 24 pixel-size bitmap!
var padding = data.Stride - (data.Width * pixelSize);
var bytes = new byte[data.Height * data.Stride];

// copy the bytes from bitmap to array
Marshal.Copy(data.Scan0, bytes, 0, bytes.Length);

var index = 0;
var builder = new StringBuilder();

for (var y = 0; y < data.Height; y++)
{
    for (var x = 0; x < data.Width; x++)
    {
        Color pixelColor = Color.FromArgb(
            pixelSize == 3 ? 255 : bytes[index + 3], // A component if present
            bytes[index + 2], // R component
            bytes[index + 1], // G component
            bytes[index]      // B component
            );

        builder
            .Append("  ")
            .Append(pixelColor.R)
            .Append("     ")
            .Append(pixelColor.G)
            .Append("     ")
            .Append(pixelColor.B)
            .Append("     ")
            .Append(pixelColor.A)
            .AppendLine();

        index += pixelSize;
    }

    index += padding;
}

// copy back the bytes from array to the bitmap
Marshal.Copy(bytes, 0, data.Scan0, bytes.Length);

textBox2.Text = builder.ToString();

Is just an example, read some good tutorials about LockBits and imaging in general to understand clearly what happens.