How to show camera preview by opengl

问题

I want to show camera preview by SurfaceTexture. I have read this sample and it work well:: Modifying camera output using SurfaceTexture and OpenGL

Now I want to do some process to the preview frames, how to get the data and push to the texture?

回答1:

There are two ways to use opengl to show this pixels data

1. Using Opengl in JAVA

2. Using opengl in c or c++ ( JNI )

Actually, either way, It is going to be easy if you know what opengl pipeline is

I alway use opengl with c++ because of reusability anyway, just follow three steps below

1. make a texture image using the preview buffer from android API (pixel is a pointer which points the camera frame buffer)

   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texture_width, texture_height, 0,GL_RGBA, GL_UNSIGNED_BYTE, pixel); 
   

2. pass the texture to shader

       glActiveTexture(GL_TEXTURE0);
       glBindTexture(GL_TEXTURE_2D, m_TextureMain);
       glUniform1i(textures[0][displayMode], 0);
   

3. process the texture at the frament shader ( texutre0 is what we just made and this code process it to grayscale image )

         static char grayscale[] = 
               "precision highp float; \n"
               "uniform sampler2D texture0;\n"
               "varying vec2 textureCoordinate;\n"
               "void main()\n"
               "{\n"
               "    float grayValue = dot(texture2D(texture0, textureCoordinate), vec4(0.3, 0.59, 0.11, 0.0));\n"
               "   gl_FragColor = vec4(grayValue, grayValue, grayValue, 1.0);\n"
               "}\n";
   

I omitted many steps which is required in opengl because It's too long such as binding, generate a framebuffer, a renderbuffer, shader settings and compile it and how to do double buffering to avoid flicking. If you don't what these are, find an example and change the three steps.

来源：https://stackoverflow.com/questions/21902490/how-to-show-camera-preview-by-opengl