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Convert Texture to GL_COMPRESSED_RGBA

I am looking for how to convert a framebuffer GL_RGBA texture to a GL_COMPRESSED_RGBA texture, preferably on a GPU. Framebuffers apparently don't have the GL_COMPRESSED_RGBA internal format, so I need a conversion method.

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If you want to perform compression on the GPU without transferring it to the CPU - here are two samples that you could convert for OpenGL (they are based on DX)

Hope this helps!

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. , OpenGL. ( - )

GLUint mytex, myrbo, myfbo;

glGenTextures(1, &mytex);
glBindTexture(GL_TEXTURE_2D, mytex);
glTexImage2D(GL_TEXTURE_2D, 0, GL_COMPRESSED_RGBA, width, height, 0,
    GL_RGBA, GL_UNSIGNED_BYTE, 0 );

glGenRenderbuffers(1, &myrbo);
glBindRenderbuffer(GL_RENDERBUFFER, myrbo);
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA, width, height)

glGenFramebuffers(1, &myfbo);
glBindFramebuffer(GL_FRAMEBUFFER, myfbo);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
    GL_RENDERBUFFER, myrbo);

// If you need a Z Buffer:
// create a 2nd renderbuffer for the framebuffer GL_DEPTH_ATTACHMENT 

// render (i.e. create the data for the texture)

// Now get the data out of the framebuffer by requesting a compressed read
glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_COMPRESSED_RGBA,
    0, 0, width, height, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindRenderbuffer(GL_RENDERBUFFER, 0);
glDeleteRenderbuffers(1, &myrbo);
glDeleteFramebuffers(1, &myfbo);

// Validate it compressed / read back compressed data
GLInt format = 0, compressed_size = 0;
glGetTexLevelParameteri(GL_TEXTURE_2D, 0, GL_TEXTURE_INTERNAL_FORMAT, &format);
glGetTexLevelParameteri(GL_TEXTURE_2D, 0, GL_TEXTURE_COMPRESSED_IMAGE_SIZE, 

char *data = malloc(compressed_size);
glGetCompressedTexImage(GL_TEXTURE_2D, 0, data);
glBindTexture(GL_TEXTURE_2D, 0);
glDeleteTexture(1, &mytex);

// data now contains the compressed thing

PBO , malloc().

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