CODEWITHSUNDEEP
bitmapf#
d.dizhevsky
d.dizhevsky

Reputation: 53

F# Creating bitmap from a memory stream throwing an exception

I'm getting 

System.ArgumentException: 'Parameter is not valid.'

for some reason.

A line where I'm getting it:

let image = Bitmap.FromStream stream

That's what I have

let ChangeBitmapColors (bitmap : Bitmap) =
Console.WriteLine bitmap.Size

let width = bitmap.Width
let height = bitmap.Height

let rectangle = new Rectangle(0, 0, width, height)

let bitmapData = bitmap.LockBits(rectangle, Imaging.ImageLockMode.ReadOnly, bitmap.PixelFormat)
let length = bitmapData.Stride * height
let bitmapArray : byte[] = Array.zeroCreate length

Marshal.Copy(bitmapData.Scan0, bitmapArray, 0, length)

bitmap.UnlockBits bitmapData

//todo something with bitmapArray

use stream = new MemoryStream(bitmapArray)                                           

let image = Bitmap.FromStream stream

stream.Dispose |> ignore

image

Any ideas what am I doing wrong here? Thanks in advance.

Upvotes: 3

Views: 315

Answers (1)

FoggyFinder
FoggyFinder

Reputation: 2220

I don't know why your code not working (I tested it and got the same result).

Another option (that works for me) it's use Marshal.UnsafeAddrOfPinnedArrayElement

let image = new Bitmap(width, height, bitmapData.Stride, bitmap.PixelFormat,Marshal.UnsafeAddrOfPinnedArrayElement(bi‌​tmapArray, 0))

Edit

Thanks @ildjarn for the explanation:

The stream didn't work because it was just raw pixel data without any image header, so there was no way to know simple things like the image dimensions and palette type. The stream approach is possible, but you need to save the image header to the stream, too, not just the scanlines

Upvotes: 3

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