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.checkState;
  
  import android.content.Context;
  import com.google.android.exoplayer2.util.FrameProcessingException;
  import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
  
  /** Provides common color filters. */
  public class RgbFilter implements RgbMatrix {
    private static final int COLOR_FILTER_GRAYSCALE_INDEX = 1;
    private static final int COLOR_FILTER_INVERTED_INDEX = 2;
  
    // Grayscale transformation matrix using the BT.709 luminance coefficients from
    // https://en.wikipedia.org/wiki/Grayscale#Converting_colour_to_grayscale
    private static final float[] FILTER_MATRIX_GRAYSCALE_SDR = {
      0.2126f, 0.2126f, 0.2126f, 0, 0.7152f, 0.7152f, 0.7152f, 0, 0.0722f, 0.0722f, 0.0722f, 0, 0, 0,
      0, 1
    };
    // Grayscale transformation using the BT.2020 primary colors from
    // https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.2020-2-201510-I!!PDF-E.pdf
    // TODO(b/241240659): Add HDR tests once infrastructure supports it.
    private static final float[] FILTER_MATRIX_GRAYSCALE_HDR = {
      0.2627f, 0.2627f, 0.2627f, 0, 0.6780f, 0.6780f, 0.6780f, 0, 0.0593f, 0.0593f, 0.0593f, 0, 0, 0,
      0, 1
    };
    // Inverted filter uses the transformation R' = -R + 1 = 1 - R.
    private static final float[] FILTER_MATRIX_INVERTED = {
      -1, 0, 0, 0, 0, -1, 0, 0, 0, 0, -1, 0, 1, 1, 1, 1
    };
  
    private final int colorFilter;
    /**
     * Ensures that the usage of HDR is consistent. {@code null} indicates that HDR has not yet been
     * set.
     */
    private @MonotonicNonNull Boolean useHdr;
  
    /** Creates a new grayscale {@code RgbFilter} instance. */
    public static RgbFilter createGrayscaleFilter() {
      return new RgbFilter(COLOR_FILTER_GRAYSCALE_INDEX);
    }
  
    /** Creates a new inverted {@code RgbFilter} instance. */
    public static RgbFilter createInvertedFilter() {
      return new RgbFilter(COLOR_FILTER_INVERTED_INDEX);
    }
  
    private RgbFilter(int colorFilter) {
      this.colorFilter = colorFilter;
    }
  
    private void checkForConsistentHdrSetting(boolean useHdr) {
      if (this.useHdr == null) {
        this.useHdr = useHdr;
      } else {
        checkState(this.useHdr == useHdr, "Changing HDR setting is not supported.");
      }
    }
  
    @Override
    public float[] getMatrix(long presentationTimeUs, boolean useHdr) {
      checkForConsistentHdrSetting(useHdr);
      switch (colorFilter) {
        case COLOR_FILTER_GRAYSCALE_INDEX:
          return useHdr ? FILTER_MATRIX_GRAYSCALE_HDR : FILTER_MATRIX_GRAYSCALE_SDR;
        case COLOR_FILTER_INVERTED_INDEX:
          return FILTER_MATRIX_INVERTED;
        default:
          // Should never happen.
          throw new IllegalStateException("Invalid color filter " + colorFilter);
      }
    }
  
    @Override
    public SingleFrameGlTextureProcessor toGlTextureProcessor(Context context, boolean useHdr)
        throws FrameProcessingException {
      checkForConsistentHdrSetting(useHdr);
      return RgbMatrix.super.toGlTextureProcessor(context, useHdr);
    }
  }
  