Optimize blur shader drawing

For external OES sampler, there is much overhead when drawing to the
window surface directly due to I/O sampling operation. So an optimized
approach is to draw the external OES sampler into FBO texture whose
resolution might be smaller than the window surface. And then we can
draw it as GLES internel sampler to the window surface with less
overhead.

There are two stages of drawing with a filter shader as external OES
sampler and another default shader as common 2D sampler.

Signed-off-by: Leo Ma <begeekmyfriend@gmail.com>

app/src/main/java/com/seu/magicfilter/base/gpuimage/GPUImageFilter.java

@@ -17,6 +17,7 @@
 package com.seu.magicfilter.base.gpuimage;
 
 import android.graphics.PointF;
+import android.opengl.GLES11Ext;
 import android.opengl.GLES20;
 
 import com.seu.magicfilter.utils.MagicFilterType;
@@ -41,6 +42,7 @@ public class GPUImageFilter {
     private final String mFragmentShader;
 
     private int mGLProgId;
+    private int mGLScreenProgId;
     private int mGLPositionIndex;
     private int mGLInputImageTextureIndex;
     private int mGLTextureCoordinateIndex;
@@ -98,6 +100,8 @@ public class GPUImageFilter {
     protected void onInit() {
         initVbo();
         mGLProgId = OpenGLUtils.loadProgram(mVertexShader, mFragmentShader);
+        mGLScreenProgId = OpenGLUtils.loadProgram(OpenGLUtils.readShaderFromRawResource(R.raw.vertex_default),
+            OpenGLUtils.readShaderFromRawResource(R.raw.fragment_default));
         mGLPositionIndex = GLES20.glGetAttribLocation(mGLProgId, "position");
         mGLTextureCoordinateIndex = GLES20.glGetAttribLocation(mGLProgId,"inputTextureCoordinate");
         mGLTextureTransformIndex = GLES20.glGetUniformLocation(mGLProgId, "textureTransform");
@@ -113,6 +117,7 @@ public class GPUImageFilter {
         destroyFboTexture();
         destoryVbo();
         GLES20.glDeleteProgram(mGLProgId);
+        GLES20.glDeleteProgram(mGLScreenProgId);
         onDestroy();
     }
 
@@ -204,7 +209,7 @@ public class GPUImageFilter {
 
         if (textureId != OpenGLUtils.NO_TEXTURE) {
             GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
-            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mGLFboTexId[0]);
+            GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId);
             GLES20.glUniform1i(mGLInputImageTextureIndex, 0);
         }
 
@@ -220,7 +225,12 @@ public class GPUImageFilter {
         return OpenGLUtils.ON_DRAWN;
     }
 
-    public int onDrawFrame() {
+    public int onDrawFrame(int cameraTextureId) {
+        int fboTexId = DrawToFboTexture(cameraTextureId);
+        return DrawToScreen(fboTexId);
+    }
+
+    private int DrawToFboTexture(int textureId) {
         if (!mIsInitialized) {
             return OpenGLUtils.NOT_INIT;
         }
@@ -243,22 +253,55 @@ public class GPUImageFilter {
         GLES20.glUniformMatrix4fv(mGLTextureTransformIndex, 1, false, mGLTextureTransformMatrix, 0);
 
         GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
-        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mGLFboTexId[0]);
+        GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textureId);
         GLES20.glUniform1i(mGLInputImageTextureIndex, 0);
 
         onDrawArraysPre();
 
-        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, mGLFboId[0]);
         GLES20.glViewport(0, 0, mInputWidth, mInputHeight);
+        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, mGLFboId[0]);
         GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
-        GLES20.glViewport(0, 0, mOutputWidth, mOutputHeight);
         GLES20.glReadPixels(0, 0, mInputWidth, mInputHeight, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, mGLFboBuffer);
         GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
-
-        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
+        GLES20.glViewport(0, 0, mOutputWidth, mOutputHeight);
 
         onDrawArraysAfter();
 
+        GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, 0);
+
+        GLES20.glDisableVertexAttribArray(mGLPositionIndex);
+        GLES20.glDisableVertexAttribArray(mGLTextureCoordinateIndex);
+
+        GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);
+
+        return mGLFboTexId[0];
+    }
+
+    private int DrawToScreen(int textureId) {
+        if (!mIsInitialized) {
+            return OpenGLUtils.NOT_INIT;
+        }
+
+        if (mGLFboId == null) {
+            return OpenGLUtils.NO_TEXTURE;
+        }
+
+        GLES20.glUseProgram(mGLScreenProgId);
+
+        GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, mGLCubeId[0]);
+        GLES20.glEnableVertexAttribArray(mGLPositionIndex);
+        GLES20.glVertexAttribPointer(mGLPositionIndex, 2, GLES20.GL_FLOAT, false, 4 * 2, 0);
+
+        GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, mGLTextureCoordinateId[0]);
+        GLES20.glEnableVertexAttribArray(mGLTextureCoordinateIndex);
+        GLES20.glVertexAttribPointer(mGLTextureCoordinateIndex, 2, GLES20.GL_FLOAT, false, 4 * 2, 0);
+
+        GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
+        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId);
+        GLES20.glUniform1i(mGLInputImageTextureIndex, 0);
+
+        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
+
         GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);
 
         GLES20.glDisableVertexAttribArray(mGLPositionIndex);