I have valid HBITMAP handle of ARGB type. How to draw it using GDI+?
I've tried method: graphics.DrawImage(Bitmap::FromHBITMAP(m_hBitmap, NULL), 0, 0); But it doesn't use alpha channel.
A:
.NET offers the static Image.FromHbitmap method. You can then use this image and invoke DrawImage on the target Graphics object.
Konrad Rudolph
2008-10-08 14:15:01
This method doesn't draw transparent color. Here is the question. How to notify Gdi+ I want to draw exactly ARGB bitmap?
2008-10-08 14:18:46
GDI+ Bitmap object has a constructor that takes Width, Height and PixelFormat as parameters. Once constructed, the bitmap will be in the desired bit depth and include an Alpha channel if requested.
Jeff B
2008-10-08 14:25:45
+1
A:
Ah... but .Net doesn't use HBITMAP and GDI+ is a C++ library atop the basic Windows GDI, so I'm assuming you're using non-.Net C++.
GDI+ has a Bitmap class, which has a FromHBITMAP() method.
Once you have the GDI+ Bitmap instance, you can use it with the GDI+ library.
Of course, if you can write your program in C# using .Net it will be a lot easier.
Jeff B
2008-10-08 14:22:02
+2
A:
I've got working sample:
// 1. Get info using bitmap handle: image size, bits
BITMAP bmpInfo;
::GetObject(m_hBitmap, sizeof(BITMAP), &bmpInfo);
int cxBitmap = bmpInfo.bmWidth;
int cyBitmap = bmpInfo.bmHeight;
void* bits = bmpInfo.bmBits;
// 2. Create & draw new GDI+ bitmap using bits with pixel format PixelFormat32bppARGB
Gdiplus::Graphics graphics(dcMemory);
Gdiplus::Bitmap bitmap(cxBitmap, cyBitmap, cxBitmap*4, PixelFormat32bppARGB, (BYTE*)bits);
graphics.DrawImage(&bitmap, 0, 0);