Windows Imaging Component & glTexImage2D()

[Kind_9]

Hello. I'm trying to load a 32 bit image with the Windows Imaging Component and use it as an opengl texture. The problem is that my code generates a runtime error from nvoglv32.dll(presumably the nvidia opengl driver).

Here is the code to load the image with WIC:

VOID GetImageFromFile(LPCWSTR file, IWICBitmap** bitmap)
{
	IWICImagingFactory* factory = NULL;
	IWICBitmapDecoder* decoder = NULL;
	IWICBitmapFrameDecode* frame = NULL;
	IWICFormatConverter* converter = NULL;
 
	CoCreateInstance(CLSID_WICImagingFactory, NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&factory));
	factory->CreateDecoderFromFilename(file, NULL, GENERIC_READ | GENERIC_WRITE, WICDecodeMetadataCacheOnDemand, &decoder);	
	decoder->GetFrame(0, &frame);
	factory->CreateFormatConverter(&converter);
	converter->Initialize(frame, GUID_WICPixelFormat32bppBGRA, WICBitmapDitherTypeNone, NULL, 0.0, WICBitmapPaletteTypeCustom);
	factory->CreateBitmapFromSource(frame, WICBitmapNoCache, bitmap);
 
	SafeRelease(factory);
	SafeRelease(decoder);
	SafeRelease(frame);
	SafeRelease(converter);
}

And here is the code that calls the above function and creates the texture:

BOOL Create(LPCWSTR file)
{
	if (!glIsEnabled(GL_TEXTURE_2D))
		glEnable(GL_TEXTURE_2D);
 
	IWICBitmap* bitmap = NULL;
	IWICBitmapLock* lock = NULL;
 
	GetImageFromFile(file, &bitmap);
        if (!bitmap)
              return FALSE;
 
	WICRect r = {0};
	bitmap->GetSize((UINT*)&r.Width, (UINT*)&r.Height);
 
	BYTE* data = NULL;
	UINT len = 0;
 
	bitmap->Lock(&r, WICBitmapLockRead, &lock);
	lock->GetDataPointer(&len, &data);
 
	UINT glid = 0;
        glGenTextures(1, &glid);
        glBindTexture(GL_TEXTURE_2D, glid);
 
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 
        glTexImage2D(GL_TEXTURE_2D, 0, 4, r.Width, r.Height, 0, GL_BGRA_EXT, GL_UNSIGNED_BYTE, data);
 
	lock->Release();
	bitmap->Release();
 
	return (GL_NO_ERROR == glGetError());
}

If I change GL_BGRA_EXT in the call to glTexImage2D() to GL_BGR_EXT everything works fine. Any ideas why this is happening? If I'm stuck using GL_BGR_EXT will the texture still be created with 4 pixel components(RGBA) as specified? I'm really getting burnt out on experimenting here and all I want is to transfer the alpha channels from the file on disk to the opengl texture.

PS. I know the code is ugly with very little error checking, but after all the experimenting I've done I'm certain that the problem lies in the call to glTexImage2D().

[Nowhere-01]

yes, the problem is in your glTexImage2D call. you should've read about it before using: http://www.opengl.org/sdk/docs/man/x...TexImage2D.xml

3-rd parameter is internalFormat, i don't know, what you meant by "4", but you can find accepted values going to the link i gave you above. in your case, it should be GL_RGBA. value 4, probably corresponds to some 3-component internal format, so in case with GL_BGRA it didn't match. and also, GL_BGRA_EXT has same value as GL_BGRA.

[Kind_9]

According to the win32 API documentation:

internalformat
The number of color components in the texture. Must be 1, 2, 3, or 4, or one of the following symbolic constants: GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16, GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8, GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4, GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16, GL_INTENSITY, GL_INTENSITY4, GL_INTENSITY8, GL_INTENSITY12, GL_INTENSITY16, GL_R3_G3_B2, GL_RGB, GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12, GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1, GL_RGBA8, GL_RGB10_A2, GL_RGBA12, or GL_RGBA16.

Besides I've already tried GL_RGB, GL_RGBA, GL_BGR, and GL_BGRA there and still get the error unless I change format to GL_RGB or GL_BGR_EXT. GL_BGRA and GL_BGR are undefined.

[Nowhere-01]

that's interesting, i can't find opengl.org spec mentioning using digits as internalformat. it says "internalFormat - Specifies the number of color components in the texture. Must be one of base internal formats given in Table 1, one of the sized internal formats given in Table 2, or one of the compressed internal formats given in Table 3, below.". and i've just tested with working code, using 3 and 4 instead of GL_RGB and GL_RGBA doesn't work.. it does work, but i wouldn't recommend that. GL_BGRA is defined in "glew.h".

so, if changing internalformat doesn't help, it most certainly crashes because "data" size is less, than width * height * 4; is your image 4 component? are you sure? re-check your code for loading image. i have no idea, what's going on there and i'd like to avoid spending my time reading doc's for this ass awful API. maybe someone else here is familiar with WIC.

[Kind_9]

I guess the number constants are Microsoft specific then. I will avoid using them. Yes I think the problem was that I was loading an image without an alpha channel, but I was assuming that WIC would add the alpha channel when converting. Anyway I used a different program to save the image with alpha and it seemed to fix it, so thank you.

[Nowhere-01]

I guess the number constants are Microsoft specific then.

what do you mean by "Microsoft specific"? they can't have their own OpenGL specification and any implementation must follow the spec. it's probably just a mistake.

[Kind_9]

Then feel free to explain why those constants are allowed. This is the beginner forum after all. I have seen plenty of examples using these constants, so either it must be part of the specification or specific to the microsoft implementation.

[Nowhere-01]

ok, my post has mistake. i've replaced wrong variables in my class. it works, you can set 1/2/3/4 as internalFormat, but i wouldn't rely on that. because i've never seen it being used like that and main specification doesn't mention that. use GL_RGB8 and GL_RGBA8.

Then feel free to explain why those constants are allowed

internalFormat argument is GLint type, which means you can pass any integer value to it. but you should only use enumerators listed in OpenGL spec.

P.S. only implementation of OpenGL Microsoft has is GDI. basically, software mode, it is used when you have no graphics card driver installed. and their implementation still must follow official specification.

[Alfonse Reinheart]

I have seen plenty of examples using these constants

If you see any code that uses a number instead of an enum for the internal format, immediately leave that website. Any such code is:

1: Poorly written.

2: Is not teaching you good OpenGL practice.

The ability to use numbers as the internal format was removed from core OpenGL in 3.1, but I'm guessing you're using the compatibility profile. Generally speaking, you should avoid any online materials that teach non-core OpenGL functionality.

[Kind_9]

I will keep that in mind, and probably I'll use the opengl.org documentation from now on. For the record though I don't normally use magic numbers like that, it was just the last thing I tried before coming here to post this.

Anyway the real issue was simpler than I thought. I was supposed to create the WIC bitmap from the format converter instead of the frame object.