Re: Loading bitmap from stream

From: Geoff Schwab [MSFT] (a-geosch_at_online.microsoft.com)
Date: 03/25/04 

Date: Thu, 25 Mar 2004 11:47:23 -0800

Hi Adam,

I have used 16 bpp bitmaps successfully but I think there is a bit of a
trick to it. The "standards" on 16 bpp bitmaps are a bit ambiguous and I
believe that only 555 RGB formatted bitmaps are supported even though these
are technically supposed to be described as 15 bpp - according to some
standards I have seen. I think you also have to have compression set to 0
even though you would think that there should be a bitmaks description.

Take a look at the following sample, it creates and loads 16 bpp bitmaps.
Not that the DIB section bmps are treated differently and actually do have a
compression setting:

Saving a Control Image to a Bitmap File
http://msdn.microsoft.com/library/en-us/dnnetcomp/html/scibf.asp 

-- 
Geoff Schwab
Program Manager
Excell Data Corporation
http://msdn.com/mobility
http://msdn.microsoft.com/mobility/prodtechinfo/devtools/netcf/FAQ/default.aspx
This posting is provided "AS IS" with no warranties, and confers no rights.
"adam" <adam@twv.org> wrote in message
news:64650689-B24C-4F91-A13B-E9E2AE82206A@microsoft.com...
> I have made some progress on this:
> The reason that the bitmap was not loading was that it was 16 bits per
pixel rather than 24 bits per pixel. It appears that whilst the compact
framework stores bitmaps (drawn within cf application as graphics) in memory
as 16bpp, it cannot read in this format. This exposes my main issue, as i am
trying to load a bitmap into an html control, from a stream.
> I currently create a new bitmap from the stream (which works if it is
24bpp), access the underlying DIBSECTION and fill the hBitmap from this in
to an INLINEIMAGEINFO struct that I then send in a message to the HTML
control. However, this is not producing a result (no image or red cross is
shown in the control).
> Does anyone know if there are restrictions on the format (esp. in terms of
bits per pixel) of the hBitmap that must be passed in the INLINEIMAGEINFO
struct?
> Am i referencing this hBitmap correctly?
>
> Thanks,
> Adam
>
> Code sample is (also uses OpenNETCF.WinAPI.Core library from
OpenNETCF.org):
>
> static CallThunk m_ct;
> protected virtual int OnNotifyMessage(ref Message m)
> {
> int iRetval = 0;
> HtmlViewMessage hvm;
> NmHdr hdr = NmHdr.GetStruct(m.LParam);
> switch (hdr.code)
> {
> case NM_INLINE_IMAGE:
> hvm = HtmlViewMessage.GetStruct(m.LParam);
> string target = hvm.target.Substring(7, hvm.target.Length - 7);//strip
"file://" from start
> if(true)//image needs handling
> {
> try
> {
> //load image represented by hvm.target
> using( FileStream fsFileHandle = File.Open(target,
System.IO.FileMode.Open) )
> {
> FileStream tempStream = new FileStream("/test.bmp",
System.IO.FileMode.Open);
> bmImage = new Bitmap(tempStream); //or new Bitmap("/test.bmp");
> }
> if(bmImage==null)
> {
> throw new Exception("Image failed to load.");
> }
> else //image successfully loaded
> {
> InMemoryBitmap imb = new InMemoryBitmap();
> // Get required Win32 callback.
> if ( m_ct == null )
> {
> IntPtr hMod = Core.GetModuleHandle("mscoree1_0");
> if ( hMod == IntPtr.Zero )
> {
> throw new Exception("Failed to get at hBitmap object.");
> }
> IntPtr pfn = Core.GetProcAddress(hMod, "NSLHandle_Reference");
> m_ct = new CallThunk(pfn, 2);
> }
>
> // Extract internal data into InMemoryBitmap object.
> IntPtr pObj = m_ct.Call(new int[] { 0x11,
Image.GetHowFromImage(bmImage).ToInt32() } );
> pObj = new IntPtr( Marshal.ReadInt32(pObj) );
> Marshal.PtrToStructure(pObj, imb);
> imgInfo.dwCookie = hvm.dwCookieFlags;
> imgInfo.iOrigHeight = imb.cx;//width
> imgInfo.iOrigWidth = imb.cy;//height
> imgInfo.hBitmap = imb.hBitmap;
> imgInfo.bOwnBitmap = false;//instructs htmlview to make own copy
> SendMessage(_hwnd, (uint)DTM_SETIMAGE, (uint)0, ref imgInfo);
> }
> }
> catch(Exception ex)
> {
> SendMessageLong(_hwnd, (IntPtr)DTM_IMAGEFAIL, (IntPtr)0,
(IntPtr)(hvm.dwCookieFlags >> 8));
> }
> iRetval = -1;
> }
> else
> {
> iRetval = 0; //default: let control handle it
> }
> break;
> }
> return iRetval;
> }
>
> private class InMemoryBitmap
> {
> internal uint dword1;
> public IntPtr hMemoryDC;
> internal uint dword2;
> internal uint dword3;
> internal uint dword4;
> internal uint dword5;
> internal uint dword6;
> public IntPtr hBitmap;
> public int cx;
> public int cy;
> }
>
> internal struct InlineImageInfo
> {
> internal UInt32 dwCookie;
> internal int iOrigHeight;
> internal int iOrigWidth;
> internal IntPtr hBitmap;
> internal bool bOwnBitmap;
> }

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