opengl es 2.0 android c++ glGetTexImage alternative

问题

when testing on windows the code works as expected, but on android the glGetTexImage api doesn't exist, is there an other way of getting all the pixels from OpenGL without caching them before creating the texture?

this is the code:

void Texture::Bind(int unit)
{
    glActiveTexture(GL_TEXTURE0 + unit);
    glBindTexture(GL_TEXTURE_2D, mTextureID);
}

GLubyte* Texture::GetPixels()
{
    Bind();

    int data_size = mWidth * mHeight * 4;

    GLubyte* pixels = new GLubyte[mWidth * mHeight * 4];

    glGetTexImage(GL_TEXTURE_2D, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

    return pixels;
}

回答1:

glGetTexImage doesn't exist in OpenGL ES.
In OpenGL ES, you have to attach the texture to a framebuffer and read the color plane from the framebuffer by glReadPixels

Bind();
int data_size = mWidth * mHeight * 4;
GLubyte* pixels = new GLubyte[mWidth * mHeight * 4];

GLuint textureObj = ...; // the texture object - glGenTextures  

GLuint fbo;
glGenFramebuffers(1, &fbo); 
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureObj, 0);

glReadPixels(0, 0, mWidth, mHeight, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

glBindFramebuffer(GL_FRAMEBUFFER, 0);
glDeleteFramebuffers(1, &fbo);

来源：https://stackoverflow.com/questions/53993820/opengl-es-2-0-android-c-glgetteximage-alternative