1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17// Extract histogram from image.
18
19package androidx.media.filterpacks.colorspace;
20
21import androidx.media.filterfw.FrameValue;
22
23import androidx.media.filterfw.Filter;
24import androidx.media.filterfw.Frame;
25import androidx.media.filterfw.FrameBuffer2D;
26import androidx.media.filterfw.FrameType;
27import androidx.media.filterfw.MffContext;
28import androidx.media.filterfw.OutputPort;
29import androidx.media.filterfw.Signature;
30
31import java.nio.ByteBuffer;
32import java.nio.ByteOrder;
33import java.nio.FloatBuffer;
34
35/**
36 * ColorfulnessFilter takes in a particular Chroma histogram generated by NewChromaHistogramFilter
37 * and compute the colorfulness based on the entropy in Hue space.
38 */
39public final class ColorfulnessFilter extends Filter {
40
41    public ColorfulnessFilter(MffContext context, String name) {
42        super(context, name);
43    }
44
45    @Override
46    public Signature getSignature() {
47        FrameType dataIn = FrameType.buffer2D(FrameType.ELEMENT_FLOAT32);
48        return new Signature()
49            .addInputPort("histogram", Signature.PORT_REQUIRED, dataIn)
50            .addOutputPort("score", Signature.PORT_REQUIRED, FrameType.single(float.class))
51            .disallowOtherPorts();
52    }
53
54    @Override
55    protected void onProcess() {
56        FrameBuffer2D histogramFrame =
57                getConnectedInputPort("histogram").pullFrame().asFrameBuffer2D();
58        ByteBuffer byteBuffer = histogramFrame.lockBytes(Frame.MODE_READ);
59        byteBuffer.order(ByteOrder.nativeOrder());
60        FloatBuffer histogramBuffer = byteBuffer.asFloatBuffer();
61        histogramBuffer.rewind();
62
63        // Create a hue histogram from hue-saturation histogram
64        int hueBins = histogramFrame.getWidth();
65        int saturationBins = histogramFrame.getHeight() - 1;
66        float[] hueHistogram = new float[hueBins];
67        float total = 0;
68        for (int r = 0; r < saturationBins; ++r) {
69            float weight = (float) Math.pow(2, r);
70            for (int c = 0; c < hueBins; c++) {
71                float value = histogramBuffer.get() * weight;
72                hueHistogram[c] += value;
73                total += value;
74            }
75        }
76        float colorful = 0f;
77        for (int c = 0; c < hueBins; ++c) {
78            float value = hueHistogram[c] / total;
79            if (value > 0f) {
80                colorful -= value * ((float) Math.log(value));
81            }
82        }
83
84        colorful /= Math.log(2);
85
86        histogramFrame.unlock();
87        OutputPort outPort = getConnectedOutputPort("score");
88        FrameValue frameValue = outPort.fetchAvailableFrame(null).asFrameValue();
89        frameValue.setValue(colorful);
90        outPort.pushFrame(frameValue);
91    }
92
93}
94