OpenGL Textures
lazarus / 70-OpenGL

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SymbolicFrank · 2015-09-05 20:47

Can anyone tell me how I can load an image, like a jpeg, and make it
into a texture that I can pass to glBindTexture?

I tried a lot of things, like the Lazarus OpenGL example, that tells
to use Vampyre for it, which doesn't compile. Like the NeHe
Texture.pas unit. Etc.

Everything else works. The shaders have the correct texture
coordinates, just not the textures that go with them.

I use the TOpenGLControl, the latest dglOpenGL.pas, TBRGABitmap for
the 2D stuff, and even glslangValidator to check the shaders.

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derek.john.evans · 2015-09-05 20:59

I use a TPicture to load a picture, and then use this code on the
TPicture.Bitmap.

Code: [Select]  glGenTextures(1, @FTexture);
  glBindTexture(GL_TEXTURE_2D, FTexture);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGBA, ABitmap.Width,
ABitmap.Height,
    lglGetPixelFormat(ABitmap.PixelFormat), GL_UNSIGNED_BYTE,
ABitmap.RawImage.Data);   


lglGetPixelFormat is this:
Code: [Select]function lglGetPixelFormat(const APixelFormat:
TPixelFormat): Integer;
begin
  case APixelFormat of
    pf24bit: begin
      Result := GL_BGR;
    end;
    pf32bit: begin
      Result := GL_BGRA;
    end;
  end;
end;

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User137 · 2015-09-05 22:37

gluBuild2DMipmaps() is not recommended, unless you are dealing with
large 3D-world. Instead glTexImage2D()

Code: [Select]glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, ABitmap.Width,
ABitmap.Height, 0,
    lglGetPixelFormat(ABitmap.PixelFormat), GL_UNSIGNED_BYTE,
ABitmap.RawImage.Data);

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SymbolicFrank · 2015-09-07 19:34

Thanks, it works.

Well, I have 4 of them, which are upside-down, but I can fix that.