Implement RGBA color matrices processor

* Transform frame colors using a defined RGBA Matrix to apply filters.

PiperOrigin-RevId: 464523581
(cherry picked from commit 23f34f8d)

library/transformer/src/main/assets/shaders/fragment_shader_transformation_es2.glsl

+#version 100
+// Copyright 2022 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// ES 2 fragment shader that samples from a (non-external) texture with
+// uTexSampler, copying from this texture to the current output while
+// applying a 4x4 RGBA color matrix to change the pixel colors.
+
+precision mediump float;
+uniform sampler2D uTexSampler;
+uniform mat4 uColorMatrix;
+varying vec2 vTexSamplingCoord;
+
+void main() {
+    vec4 inputColor = texture2D(uTexSampler, vTexSamplingCoord);
+    gl_FragColor = uColorMatrix * inputColor;
+}

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/RgbaMatrix.java

+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.android.exoplayer2.transformer;
+
+import android.content.Context;
+import androidx.media3.common.FrameProcessingException;
+
+/**
+ * Specifies a 4x4 RGBA color transformation matrix to apply to each frame in the fragment shader.
+ */
+public interface RgbaMatrix extends GlEffect {
+
+  /**
+   * Returns the 4x4 RGBA transformation {@linkplain android.opengl.Matrix matrix} to apply to the
+   * color values of each pixel in the frame with the given timestamp.
+   */
+  float[] getMatrix(long presentationTimeUs);
+
+  @Override
+  default RgbaMatrixProcessor toGlTextureProcessor(Context context, boolean useHdr)
+      throws FrameProcessingException {
+    return new RgbaMatrixProcessor(context, /* rgbaMatrix= */ this, useHdr);
+  }
+}

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/RgbaMatrixProcessor.java

+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.android.exoplayer2.transformer;
+
+import android.content.Context;
+import android.opengl.GLES20;
+import android.opengl.Matrix;
+import android.util.Pair;
+import androidx.media3.common.FrameProcessingException;
+import com.google.android.exoplayer2.util.GlProgram;
+import com.google.android.exoplayer2.util.GlUtil;
+import java.io.IOException;
+
+/** Applies an {@link RgbaMatrix} to each frame. */
+/* package */ final class RgbaMatrixProcessor extends SingleFrameGlTextureProcessor {
+  private static final String VERTEX_SHADER_PATH = "shaders/vertex_shader_transformation_es2.glsl";
+  private static final String FRAGMENT_SHADER_PATH =
+      "shaders/fragment_shader_transformation_es2.glsl";
+
+  private final GlProgram glProgram;
+  private final RgbaMatrix rgbaMatrix;
+
+  // TODO(b/239431666): Support chaining multiple RgbaMatrix instances in RgbaMatrixProcessor.
+  // TODO(b/239757183): Merge RgbaMatrixProcessor with MatrixTransformationProcessor.
+  public RgbaMatrixProcessor(Context context, RgbaMatrix rgbaMatrix, boolean useHdr)
+      throws FrameProcessingException {
+    super(useHdr);
+    this.rgbaMatrix = rgbaMatrix;
+
+    try {
+      glProgram = new GlProgram(context, VERTEX_SHADER_PATH, FRAGMENT_SHADER_PATH);
+    } catch (IOException | GlUtil.GlException e) {
+      throw new FrameProcessingException(e);
+    }
+
+    // Draw the frame on the entire normalized device coordinate space, from -1 to 1, for x and y.
+    glProgram.setBufferAttribute(
+        "aFramePosition",
+        GlUtil.getNormalizedCoordinateBounds(),
+        GlUtil.HOMOGENEOUS_COORDINATE_VECTOR_SIZE);
+
+    float[] identityMatrix = new float[16];
+    Matrix.setIdentityM(identityMatrix, /* smOffset= */ 0);
+    glProgram.setFloatsUniform("uTransformationMatrix", identityMatrix);
+    glProgram.setFloatsUniform("uTexTransformationMatrix", identityMatrix);
+  }
+
+  @Override
+  public Pair<Integer, Integer> configure(int inputWidth, int inputHeight) {
+    return Pair.create(inputWidth, inputHeight);
+  }
+
+  @Override
+  public void drawFrame(int inputTexId, long presentationTimeUs) throws FrameProcessingException {
+    float[] rgbaMatrixArray = rgbaMatrix.getMatrix(presentationTimeUs);
+    try {
+      glProgram.use();
+      glProgram.setSamplerTexIdUniform("uTexSampler", inputTexId, /* texUnitIndex= */ 0);
+      glProgram.setFloatsUniform("uColorMatrix", rgbaMatrixArray);
+      glProgram.bindAttributesAndUniforms();
+
+      // The four-vertex triangle strip forms a quad.
+      GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, /* first= */ 0, /* count= */ 4);
+    } catch (GlUtil.GlException e) {
+      throw new FrameProcessingException(e, presentationTimeUs);
+    }
+  }
+}