content: /*
   * 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.effect;
  
  import static com.google.android.exoplayer2.util.Assertions.checkArgument;
  
  import android.content.Context;
  import android.opengl.GLES20;
  import android.util.Pair;
  import com.google.android.exoplayer2.util.FrameProcessingException;
  import com.google.android.exoplayer2.util.GlProgram;
  import com.google.android.exoplayer2.util.GlUtil;
  import java.io.IOException;
  
  /** Applies the {@link HslAdjustment} to each frame in the fragment shader. */
  /* package */ final class HslProcessor 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_hsl_es2.glsl";
  
    private final GlProgram glProgram;
  
    /**
     * Creates a new instance.
     *
     * @param context The {@link Context}.
     * @param hslAdjustment The {@link HslAdjustment} to apply to each frame in order.
     * @param useHdr Whether input textures come from an HDR source. If {@code true}, colors will be
     *     in linear RGB BT.2020. If {@code false}, colors will be in linear RGB BT.709.
     * @throws FrameProcessingException If a problem occurs while reading shader files.
     */
    public HslProcessor(Context context, HslAdjustment hslAdjustment, boolean useHdr)
        throws FrameProcessingException {
      super(useHdr);
      // TODO(b/241241680): Check if HDR <-> HSL works the same or not.
      checkArgument(!useHdr, "HDR is not yet supported.");
  
      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 = GlUtil.create4x4IdentityMatrix();
      glProgram.setFloatsUniform("uTransformationMatrix", identityMatrix);
      glProgram.setFloatsUniform("uTexTransformationMatrix", identityMatrix);
  
      // OpenGL operates in a [0, 1] unit range and thus we transform the HSL intervals into
      // the unit interval as well. The hue is defined in the [0, 360] interval and saturation
      // and lightness in the [0, 100] interval.
      glProgram.setFloatUniform("uHueAdjustmentDegrees", hslAdjustment.hueAdjustmentDegrees / 360);
      glProgram.setFloatUniform("uSaturationAdjustment", hslAdjustment.saturationAdjustment / 100);
      glProgram.setFloatUniform("uLightnessAdjustment", hslAdjustment.lightnessAdjustment / 100);
    }
  
    @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 {
      try {
        glProgram.use();
        glProgram.setSamplerTexIdUniform("uTexSampler", inputTexId, /* texUnitIndex= */ 0);
        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);
      }
    }
  }
  