opengl es 2.0 android c ++ glGetTexImage替代 [英] opengl es 2.0 android c++ glGetTexImage alternative

问题描述

在Windows上进行测试时，代码可以按预期工作，但是在android上，不存在glGetTexImage api，是否还有另一种方法可以从OpenGL获取所有像素，而无需在创建纹理之前对其进行缓存?

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?

这是代码:

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;
}

推荐答案

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);

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