# OpenGL wxImage::GetAlpha and OpenGL

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Hello, As I understand it wxImage::GetData() returns *uchar[3] (RGB) and wxImage::GetAlpha() returns *uchar[1](A). I am using a wxGLCanvas and to load textures I have this function
def LoadTexture(tex_src , tex_id , size):
tex_id[0] = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, tex_id[0])

glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)

wximage = wxImage(tex_src)

size.append(wximage.GetWidth())
size.append(wximage.GetHeight())

# i think OpenGL does this for us...
# either way OpenGL resize is faster & easier
#if not isCompliant(glImage))
#	glImage = makeGLCompliant(glImage);

# how to get the alpha channel together with pixel data
if wximage.HasAlpha():
glTexImage2D(GL_TEXTURE_2D , 0 , GL_RGB , wximage.GetWidth(),
wximage.GetHeight() , 0 , GL_RGB , GL_UNSIGNED_BYTE , wximage.GetData())
else:
glTexImage2D(GL_TEXTURE_2D , 0 , GL_RGB , wximage.GetWidth(),
wximage.GetHeight() , 0 , GL_RGB , GL_UNSIGNED_BYTE , wximage.GetData())

return tex_id


Any clues on how I can load the image alpha into OpenGL (GL_RGBA) without cocantenating a new pixel array O_O?

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There is no decent way to do that. The way wxImage stores Alpha in a seperate buffer makes this a problem. You need to make a new buffer and interleave the RGB and the A into the one buffer, and give that to glTexImage2D().

Or use something else to load the images, like DevIL.

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ok, thank you very much.

I already have an SDL loader, but wanted to reduce the SDL dependency.
This is just what I thought :P

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