Byte of pixel data to image

Question

I have learnt how to export pixel data of an image to byte array, here is my code

void Button2Click(object sender, EventArgs e)
{
    Bitmap img = new Bitmap (@"24x30.bmp");
    var BitmapData = img.LockBits( new Rectangle(0,0,img.Width,img.Height),ImageLockMode.ReadOnly,img.PixelFormat);
    var length = BitmapData.Stride * BitmapData.Height;
    MessageBox.Show(BitmapData.Width.ToString());
    byte[] bytes = new byte[length];
    Marshal.Copy(BitmapData.Scan0, bytes, 0, length);
    img.UnlockBits(BitmapData);
    string test = ByteArrayToBinary(bytes);
}

I convert the bytes to string bit but lets ignore it. What I want to know is, how can I convert the byte of pixel data to an image? Please share the code and the reference.

I have read many references but I don't get it until now.

EDIT:

This summary of my case, i have Stride, Width, Height, and Byte[] of Pixel data. How can i reconstruct it to image again thanks

If you have a `Bitmap`, you already have an image. `Bitmap` extends `Image`. So why are you trying to remake it? — Patrick Roberts, Apr 15 '18 at 07:25
i want to convert my image to byte and then i convert it to bit. in another case i have to reconstruct the bits to byte and then to the image again. but i stuck with reconstruct code. — Jackuze, Apr 15 '18 at 07:32
You can use BitmapEncoder and save the Bitmap using a Stream. — Jean-Claude Colette, Apr 15 '18 at 07:52
byte[], i have tried use BitmapEncoder but it cant be used because my byte array just contain pixel data there is no header or file type. — Jackuze, Apr 15 '18 at 08:10
@Jackuze If you have `Stride`, `Width`, `Height`, and `Byte[]`, you're still missing `PixelFormat`. Once you have that, see the method I linked in my answer. — Nyerguds, May 24 '18 at 06:56

score 1 · Answer 1 · answered Apr 15 '18 at 10:27

1

Same code, but copy the other way. (You can read a dummy image or use another image constructor.)

answered Apr 15 '18 at 10:27

Sorry, please enlight meee – Jackuze Apr 15 '18 at 10:54
Nonsense. The byte array itself is insufficient; it's lacking all header information concerning the image dimensions and pixel format. – Nyerguds Jan 02 '19 at 12:30
@Nyerguds: you didn't understand my answer. – Jan 02 '19 at 12:40
Not surprising; you barely gave one. – Nyerguds Jan 02 '19 at 13:03

Nyerguds · Answer 2 · 2018-04-16T08:07:08.430

Obviously, you first step should be to somehow convert your text back to a byte array, but then you'll see that you can't actually create an image from just that data.

As you mentioned in comments already, your dumped binary block is missing all header data. You need the original width, height and pixel format before you can convert the data back to an image.

Also, if this is an indexed image, there will be a colour palette, and you don't save that either.

And finally, you copy all data in the image memory. Images are kept in memory per line of pixels, but these lines are usually rounded to the next multiple of four bytes (except in some indexed pixel formats, I think). This means that unless your image uses four bytes per pixel (32 bits per pixel), the bytes you end up with may contain junk data at the end of each line. You don't trim that off in any way, meaning you not only need the width and height, but the stride as well, before you can reconstruct the image.

As for how to build the image, the method is pretty much the same. You make a new image with the correct dimensions and pixel format, open its backing memory using LockBits but in WriteOnly mode, and copy your data into it.

I posted a full method for that on this site before, so feel free to check it out.

Byte of pixel data to image

2 Answers2