Android OpenGL: How to change bitmap attached to texture?

Question

I have created a texture like this

public int createTexture(Bitmap bitmap){
 final int[] textureHandle = new int[1];
 GLES20.glGenTextures(1, textureHandle, 0);
 glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]);       
 glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
 glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_NEAREST);
 // Load the bitmap into the bound texture.
 GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0); 
 return textureHandle[0];
}

Now based on the user input I want to update my Texture with the new Bitmap . I tried recalling same function with different Bitmap but its not getting updated. Am I doing something wrong here?

EDIT

I tried as Tommy said in his answer but no use. Let me elaborate how I am using textures.

public void changeFilter(){
  //create required bitmap here
  if(mTextureDataHandle1==0) 
    mTextureDataHandle1 =loadTexture(bitmap); 
  else 
      updateTexture(mTextureDataHandle1);
}

In onDrawFrame

 glActiveTexture(GL_TEXTURE1);
 glBindTexture(GL_TEXTURE_2D, mTextureDataHandle1);
 glUniform1i(mTextureUniformHandle1, 1);

Answer 1

That method both creates a new texture and uploads a Bitmap to it. It sounds like you want to do the second thing but not the first? If so then provide the int texture name as a parameter rather than receiving it as a result, and skip straight to the glBindTexure (ie omit the glGenTextures , which is what creates the new texture).

Eg

public int createTexture(Bitmap bitmap){
 final int[] textureHandle = new int[1];
 GLES20.glGenTextures(1, textureHandle, 0);
 glBindTexture(GLES20.GL_TEXTURE_2D, textureName);       
 glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
 glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_NEAREST);
 updateTexture(textureHandle[0], bitmap);
 return textureHandle[0];
}

public void updateTexture(int textureName, Bitmap bitmap) {
 glBindTexture(GLES20.GL_TEXTURE_2D, textureName);       
 // Load the bitmap into the bound texture.
 GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0); 
}

So the bit where you upload a Bitmap is factored out from the bit where you create a texture and set its filtering type; to update an existing texture use the int you got earlier and call directly into updateTexture .

Answer 2

You may simply be not on the OpenGL rendering thread when changing the Bitmap. When you change the Bitmap, save in a boolean that you did so, and then only in the rendering thread call texImage2D.

Answer 3

I tried the techniques in the above responses I got horrible performance. If what you want is to update the texture live as in 60 fps there is a better way. BTW I didn't find documentation on it, I had to pull and pieces together from different sources.

(1) you have to tell OpenGL extensions to use external textures. That is when defining your texture instead of using GLES20.GL_TEXTURE0 you use GLES11Ext.GL_TEXTURE_EXTERNAL_OES

(2) you have to use the classes Surface and SurfaceTexture. (look into consumers and producers for more into. They work like a server/client but instead the architecture is called consumer/producer)

(3) You have to enable an extension on your fragment shader. You can't use sampler2D you have to use samplerExternalOES . To enable the extension you put the following line at the top of your shader code:

#extension GL_OES_EGL_image_external: require

Code snapshot

The above is a snapshot of my code, below is the fragment shader

Fragment shader