create HICON from memory on windows

Question

I have the contents of a .ico file in memory as a const char*, and I wish to create a HICON from this data. My current approach is to write the data to a temporary file and then use LoadImage. Is it possible to instead create the icon directly from memory?

@DavidHeffernan I'm trying to avoid creating a file. I have the contents of the icon in memory as a character array and wish to create a HICON directly from that data. — Alex Flint, Feb 10 '17 at 19:32
https://referencesource.microsoft.com/#System.Drawing/commonui/System/Drawing/Icon.cs,e01910ea8cd8d6a8 — Hans Passant, Feb 10 '17 at 19:42
So don't create a file. Parse the content and create the icon. — David Heffernan, Feb 10 '17 at 19:59
@DavidHeffernan Thanks - my question is about how to do exactly that. — Alex Flint, Feb 10 '17 at 20:02
There are plenty of articles on the ico format. Read them and take it from there. — David Heffernan, Feb 10 '17 at 20:38
If you can use [GDI+](https://msdn.microsoft.com/en-us/library/ms533798.aspx), you can wrap the raw ICO data in an `IStream` using `CreateStreamOnHGlobal()` or `SHCreateMemStream()`, and then pass that stream to the `Bitmap` class constructor or `Bitmap::FromStream()` method, and then finally call the `Bitmap::ToHICON()` method. — Remy Lebeau, Feb 11 '17 at 03:34

score 3 · Answer 1 · answered Mar 04 '18 at 21:13

With CreateIcon you can certainly create icons but I'm not really sure you can feed it with a png-format image data.

I had success with CreateIconFromResourceEx (sorry for using other language, but take it as an example, you can use that function directly in C) :

from ctypes import *
from ctypes.wintypes import *
CreateIconFromResourceEx = windll.user32.CreateIconFromResourceEx

size_x, size_y = 32, 32 LR_DEFAULTCOLOR = 0

with open("my32x32.png", "rb") as f:
    png = f.read()
hicon = CreateIconFromResourceEx(png, len(png), 1, 0x30000, size_x, size_y, LR_DEFAULTCOLOR)

Hope it helps you.

score 2 · Accepted Answer · answered Feb 27 '17 at 03:54

If you want to do this without using GDI+ nor WIC then you have to do some parsing yourself because the format of a .ICO file is not exactly the same as a icon resource in a .EXE/.DLL so you cannot use the resource based icon functions. The official binary spec can be found here and there is a great blog series about it here.

If your .ico file has more than one image in it then you must loop over the icon directories until you find a image dimension you are happy with. You can then call CreateIcon to create a HICON.

create HICON from memory on windows

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