Create Bitmap object from array

Question

I have an array like byte[] pixels. Is there any way to create a bitmap object from that pixels without copying data? I have a small graphics library, when I need to display image on WinForms window I just copy that data to a bitmap object, then I use draw method. Can I avoid this copying process? I remember I saw it somewhere, but maybe my memory is just bad.

Edit: I tried this code and it works, but is this safe?

byte[] pixels = new byte[10 * 10 * 4];

pixels[4] = 255; // set 1 pixel
pixels[5] = 255;
pixels[6] = 255;
pixels[7] = 255;

// do some tricks
GCHandle pinnedArray = GCHandle.Alloc(pixels, GCHandleType.Pinned);
IntPtr pointer = pinnedArray.AddrOfPinnedObject();

// create a new bitmap.
Bitmap bmp = new Bitmap (10, 10, 4*10, PixelFormat.Format32bppRgb, pointer);

Graphics grp = this.CreateGraphics ();
grp.DrawImage (bmp, 0, 0);

pixels[4+12] = 255; // add a pixel
pixels[5+12] = 255;
pixels[6+12] = 255;
pixels[7+12] = 255;

grp.DrawImage (bmp, 0, 40);

This is somewhat related I think: stackoverflow.com/questions/1580130/… — Patrick
– Patrick, Commented Aug 16, 2012 at 14:52

Timbo · Accepted Answer · 2012-08-16 15:19:57Z

6

There is a constructor that takes a pointer to raw image data:

Bitmap Constructor (Int32, Int32, Int32, PixelFormat, IntPtr)

Example:

byte[] _data = new byte[]
{
    255, 0, 0, 255, // Blue
    0, 255, 0, 255, // Green
    0, 0, 255, 255, // Red
    0, 0, 0, 255,   // Black
};

var arrayHandle = System.Runtime.InteropServices.GCHandle.Alloc(_data,
        System.Runtime.InteropServices.GCHandleType.Pinned);

var bmp = new Bitmap(2, 2, // 2x2 pixels
    8,                     // RGB32 => 8 bytes stride
    System.Drawing.Imaging.PixelFormat.Format32bppArgb,
    arrayHandle.AddrOfPinnedObject()
);

this.BackgroundImageLayout = ImageLayout.Stretch;
this.BackgroundImage = bmp;

edited Aug 16, 2012 at 15:19

answered Aug 16, 2012 at 14:39

Timbo

28.2k11 gold badges52 silver badges75 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

apocalypse Over a year ago

When I try to draw newBitmap it throws Access Violation :/ It says it should be called from Paint method (PaintEventArgs).

Joshua · Accepted Answer · 2012-08-16 14:51:28Z

0

Couldn't you just use:

System.Drawing.Bitmap.FromStream(new MemoryStream(bytes));

I don't think these method calls will do any copying, as nothing in the MSDN indicate such: http://msdn.microsoft.com/en-us/library/9a84386f

answered Aug 16, 2012 at 14:51

Joshua

4,17927 silver badges38 bronze badges

1 Comment

Mozzis Over a year ago

A lot of people seem to miss the fact that the FromStream method expects that the stream will contain the bitmap header info along with the RGB or pixel values.

Collectives™ on Stack Overflow

Create Bitmap object from array

2 Answers 2

1 Comment

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related