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dotnet drawing api : HEEEELP: Getting a BITMAPINFOHEADER ptr out of .NET Bitmap class - HOW?
load a BITMAPINFOHEADER data pointer into a Bitmap object. The way I did it was to use a MemoryStream in the Bitmap constructor. I am assuming that you could do the reverse using the Bitmap.Save method. One thing that I found out on loading an image is that the Bitmap object expects a BITMAPFILEHEADER to precede the BITMAPINFOHEADER when loading the bitmap. Here is my suggestion for extracting the BITMAPINFOHEADER, but I can't say for sure if this would work because I have not tried it. 1. Create a MemoryStream object. 2. Call the Bitmap.Save() method passing the MemoryStream object from step 1. You may need to specify the BMP coded for the save. 3. Read the MemoryStream contents into a byte array (MemoryStream.Read or MemoryStream.ToArray). 4. Pin the first element of the byte array to a C++ memory pointer. 5. Parse the memory pointer for the BITMAPINFOHEADER. Note that a BITMAPFILEHEADER will probably be at the start of the bitmap memory pointer. You probably need to offset past that header. 6. Send the BITMAPINFOHEADER pointer to your function that requires it. -- ----------------------------------- Ken Varn Senior Software Engineer Diebold Inc. varnk@diebold.com ----------------------------------- [quoted text, click to view] "José Joye" <jose.joye@KILLTHESPAMSbluewin.ch> wrote in message news:%231yQ9HWQDHA.3144@tk2msftngp13.phx.gbl... > Hello, > > In my Managed C++ code, I have an instance of the .NET Bitmap class and I > need to call a non managed routine within a third party library which expect > a a pointer to BITMAPINFOHEADER > > Is there a simple way to get this information out of the .NET Bitmap class? > > I know of the: > IntPtr hBitmap = BM->GetHbitmap(); > > However, it sounds like a nightmare to go from this point on to my target. > > Does anyone has a working sample. I googled for hours and I still do not see > how to proceed. > > Thanks, > José > >
Hello,
In my Managed C++ code, I have an instance of the .NET Bitmap class and I need to call a non managed routine within a third party library which expect a a pointer to BITMAPINFOHEADER Is there a simple way to get this information out of the .NET Bitmap class? I know of the: IntPtr hBitmap = BM->GetHbitmap(); However, it sounds like a nightmare to go from this point on to my target. Does anyone has a working sample. I googled for hours and I still do not see how to proceed. Thanks, José
Hi,
In fact, Idid have already the stream in memory. But I did not know what to do with it. Therefore, I tried to push it in the CTOR of the Bitmap ... not too clever... q:-) I followed your explanation up to : "You probably need to offset past that header" What do you mean by that? José [quoted text, click to view] "Ken Varn" <varnk@diebold.com> wrote in message news:%23%23EH00WQDHA.1072@TK2MSFTNGP10.phx.gbl... > I have had to do something similar to what you are describing. I had to > load a BITMAPINFOHEADER data pointer into a Bitmap object. The way I did it > was to use a MemoryStream in the Bitmap constructor. I am assuming that you > could do the reverse using the Bitmap.Save method. One thing that I found > out on loading an image is that the Bitmap object expects a BITMAPFILEHEADER > to precede the BITMAPINFOHEADER when loading the bitmap. > > Here is my suggestion for extracting the BITMAPINFOHEADER, but I can't say > for sure if this would work because I have not tried it. > > 1. Create a MemoryStream object. > 2. Call the Bitmap.Save() method passing the MemoryStream object from step > 1. You may need to specify the BMP coded for the save. > 3. Read the MemoryStream contents into a byte array (MemoryStream.Read or > MemoryStream.ToArray). > 4. Pin the first element of the byte array to a C++ memory pointer. > 5. Parse the memory pointer for the BITMAPINFOHEADER. Note that a > BITMAPFILEHEADER will probably be at the start of the bitmap memory pointer. > You probably need to offset past that header. > 6. Send the BITMAPINFOHEADER pointer to your function that requires it. > > > -- > ----------------------------------- > Ken Varn > Senior Software Engineer > Diebold Inc. > varnk@diebold.com > ----------------------------------- > "José Joye" <jose.joye@KILLTHESPAMSbluewin.ch> wrote in message > news:%231yQ9HWQDHA.3144@tk2msftngp13.phx.gbl... > > Hello, > > > > In my Managed C++ code, I have an instance of the .NET Bitmap class and I > > need to call a non managed routine within a third party library which > expect > > a a pointer to BITMAPINFOHEADER > > > > Is there a simple way to get this information out of the .NET Bitmap > class? > > > > I know of the: > > IntPtr hBitmap = BM->GetHbitmap(); > > > > However, it sounds like a nightmare to go from this point on to my target. > > > > Does anyone has a working sample. I googled for hours and I still do not > see > > how to proceed. > > > > Thanks, > > José > > > > > >
Generally, Windows bitmap files contain a BITMAPFILEHEADER that is the first
record. Immediately after this header is the BITMAPINFOHEADER. So, if you save the image in windows bitmap format, the image data looks something like this: BITMAPFILEHEADER BITMAPINFOHEADER Raw Bitmap Data Check your MSDN standard Windows GDI section for a description of these two headers. Note that Microsoft also has a structure defined called BITMAPINFO. This structure is laid out as follows: struct BITMAPINFO { BITMAPINFOHEADER bmiHeader; RGBQUAD bmiColors[1]; }; This structure is interesting in that it allows you to point it to a bitmap block to get the header that follows the BITMAPFILEHEADER, and the image bytes that follow. The RGBQUAD section is variable length and can contain as many records as is indicated by the bmiHeader. You would think there would be one structure to handle both BITMAPFILEHADER and BITMAPINFOHEADER, but since there are different versions of the lengths of these structures, there is no way to utilize a structure to accommodate them. There are so many variations on how BITMAPINFO is used, that it would take awhile to explain the ones that I know in an e-mail. Some elements point to offsets that get you to other sections of the data. Look in MSDN or search on the web. There is a lot of information on how these data blocks are used for various image formats. -- ----------------------------------- Ken Varn Senior Software Engineer Diebold Inc. varnk@diebold.com ----------------------------------- [quoted text, click to view] "José Joye" <jose.joye@KILLTHESPAMSbluewin.ch> wrote in message news:OOHCqBXQDHA.2636@TK2MSFTNGP10.phx.gbl... > Hi, > > In fact, Idid have already the stream in memory. But I did not know what to > do with it. Therefore, I tried to push it in the CTOR of the Bitmap ... not > too clever... q:-) > > I followed your explanation up to : "You probably need to offset past that > header" > What do you mean by that? > > José > > "Ken Varn" <varnk@diebold.com> wrote in message > news:%23%23EH00WQDHA.1072@TK2MSFTNGP10.phx.gbl... > > I have had to do something similar to what you are describing. I had to > > load a BITMAPINFOHEADER data pointer into a Bitmap object. The way I did > it > > was to use a MemoryStream in the Bitmap constructor. I am assuming that > you > > could do the reverse using the Bitmap.Save method. One thing that I found > > out on loading an image is that the Bitmap object expects a > BITMAPFILEHEADER > > to precede the BITMAPINFOHEADER when loading the bitmap. > > > > Here is my suggestion for extracting the BITMAPINFOHEADER, but I can't say > > for sure if this would work because I have not tried it. > > > > 1. Create a MemoryStream object. > > 2. Call the Bitmap.Save() method passing the MemoryStream object from > step > > 1. You may need to specify the BMP coded for the save. > > 3. Read the MemoryStream contents into a byte array (MemoryStream.Read or > > MemoryStream.ToArray). > > 4. Pin the first element of the byte array to a C++ memory pointer. > > 5. Parse the memory pointer for the BITMAPINFOHEADER. Note that a > > BITMAPFILEHEADER will probably be at the start of the bitmap memory > pointer. > > You probably need to offset past that header. > > 6. Send the BITMAPINFOHEADER pointer to your function that requires it. > > > > > > -- > > ----------------------------------- > > Ken Varn > > Senior Software Engineer > > Diebold Inc. > > varnk@diebold.com > > ----------------------------------- > > "José Joye" <jose.joye@KILLTHESPAMSbluewin.ch> wrote in message > > news:%231yQ9HWQDHA.3144@tk2msftngp13.phx.gbl... > > > Hello, > > > > > > In my Managed C++ code, I have an instance of the .NET Bitmap class and > I > > > need to call a non managed routine within a third party library which > > expect > > > a a pointer to BITMAPINFOHEADER > > > > > > Is there a simple way to get this information out of the .NET Bitmap > > class? > > > > > > I know of the: > > > IntPtr hBitmap = BM->GetHbitmap(); > > > > > > However, it sounds like a nightmare to go from this point on to my > target. > > > > > > Does anyone has a working sample. I googled for hours and I still do not > > see > > > how to proceed. > > > > > > Thanks, > > > José > > > > > > > > > > > >
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