/*
 * Copyright (C) 2007 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 android.graphics;

import java.util.Arrays;

4x5 matrix for transforming the color and alpha components of a Bitmap.
The matrix can be passed as single array, and is treated as follows:
 [ a, b, c, d, e,
   f, g, h, i, j,
   k, l, m, n, o,
   p, q, r, s, t ]

When applied to a color [R, G, B, A], the resulting color
is computed as:

  R’ = a*R + b*G + c*B + d*A + e;
  G’ = f*R + g*G + h*B + i*A + j;
  B’ = k*R + l*G + m*B + n*A + o;
  A’ = p*R + q*G + r*B + s*A + t;

That resulting color [R’, G’, B’, A’]
then has each channel clamped to the 0 to 255
range.


The sample ColorMatrix below inverts incoming colors by scaling each
channel by -1, and then shifting the result up by
255 to remain in the standard color space.

  [ -1, 0, 0, 0, 255,
    0, -1, 0, 0, 255,
    0, 0, -1, 0, 255,
    0, 0, 0, 1, 0 ]
/**
 * 4x5 matrix for transforming the color and alpha components of a Bitmap.
 * The matrix can be passed as single array, and is treated as follows:
 *
 * <pre>
 *  [ a, b, c, d, e,
 *    f, g, h, i, j,
 *    k, l, m, n, o,
 *    p, q, r, s, t ]</pre>
 *
 * <p>
 * When applied to a color <code>[R, G, B, A]</code>, the resulting color
 * is computed as:
 * </p>
 *
 * <pre>
 *   R&rsquo; = a*R + b*G + c*B + d*A + e;
 *   G&rsquo; = f*R + g*G + h*B + i*A + j;
 *   B&rsquo; = k*R + l*G + m*B + n*A + o;
 *   A&rsquo; = p*R + q*G + r*B + s*A + t;</pre>
 *
 * <p>
 * That resulting color <code>[R&rsquo;, G&rsquo;, B&rsquo;, A&rsquo;]</code>
 * then has each channel clamped to the <code>0</code> to <code>255</code>
 * range.
 * </p>
 *
 * <p>
 * The sample ColorMatrix below inverts incoming colors by scaling each
 * channel by <code>-1</code>, and then shifting the result up by
 * <code>255</code> to remain in the standard color space.
 * </p>
 *
 * <pre>
 *   [ -1, 0, 0, 0, 255,
 *     0, -1, 0, 0, 255,
 *     0, 0, -1, 0, 255,
 *     0, 0, 0, 1, 0 ]</pre>
 */
@SuppressWarnings({ "MismatchedReadAndWriteOfArray", "PointlessArithmeticExpression" })
public class ColorMatrix {
    private final float[] mArray = new float[20];

    
Create a new colormatrix initialized to identity (as if reset() had
been called).
/**
     * Create a new colormatrix initialized to identity (as if reset() had
     * been called).
     */
    public ColorMatrix() {
        reset();
    }

    
Create a new colormatrix initialized with the specified array of values.
/**
     * Create a new colormatrix initialized with the specified array of values.
     */
    public ColorMatrix(float[] src) {
        System.arraycopy(src, 0, mArray, 0, 20);
    }

    
Create a new colormatrix initialized with the specified colormatrix.
/**
     * Create a new colormatrix initialized with the specified colormatrix.
     */
    public ColorMatrix(ColorMatrix src) {
        System.arraycopy(src.mArray, 0, mArray, 0, 20);
    }

    
Return the array of floats representing this colormatrix.
/**
     * Return the array of floats representing this colormatrix.
     */
    public final float[] getArray() { return mArray; }

    
Set this colormatrix to identity:
[ 1 0 0 0 0   - red vector
  0 1 0 0 0   - green vector
  0 0 1 0 0   - blue vector
  0 0 0 1 0 ] - alpha vector

/**
     * Set this colormatrix to identity:
     * <pre>
     * [ 1 0 0 0 0   - red vector
     *   0 1 0 0 0   - green vector
     *   0 0 1 0 0   - blue vector
     *   0 0 0 1 0 ] - alpha vector
     * </pre>
     */
    public void reset() {
        final float[] a = mArray;
        Arrays.fill(a, 0);
        a[0] = a[6] = a[12] = a[18] = 1;
    }

    
Assign the src colormatrix into this matrix, copying all of its values.
/**
     * Assign the src colormatrix into this matrix, copying all of its values.
     */
    public void set(ColorMatrix src) {
        System.arraycopy(src.mArray, 0, mArray, 0, 20);
    }

    
Assign the array of floats into this matrix, copying all of its values.
/**
     * Assign the array of floats into this matrix, copying all of its values.
     */
    public void set(float[] src) {
        System.arraycopy(src, 0, mArray, 0, 20);
    }

    
Set this colormatrix to scale by the specified values.
/**
     * Set this colormatrix to scale by the specified values.
     */
    public void setScale(float rScale, float gScale, float bScale,
                         float aScale) {
        final float[] a = mArray;

        for (int i = 19; i > 0; --i) {
            a[i] = 0;
        }
        a[0] = rScale;
        a[6] = gScale;
        a[12] = bScale;
        a[18] = aScale;
    }

    
Set the rotation on a color axis by the specified values.

axis=0 correspond to a rotation around the RED color
axis=1 correspond to a rotation around the GREEN color
axis=2 correspond to a rotation around the BLUE color

/**
     * Set the rotation on a color axis by the specified values.
     * <p>
     * <code>axis=0</code> correspond to a rotation around the RED color
     * <code>axis=1</code> correspond to a rotation around the GREEN color
     * <code>axis=2</code> correspond to a rotation around the BLUE color
     * </p>
     */
    public void setRotate(int axis, float degrees) {
        reset();
        double radians = degrees * Math.PI / 180d;
        float cosine = (float) Math.cos(radians);
        float sine = (float) Math.sin(radians);
        switch (axis) {
        // Rotation around the red color
        case 0:
            mArray[6] = mArray[12] = cosine;
            mArray[7] = sine;
            mArray[11] = -sine;
            break;
        // Rotation around the green color
        case 1:
            mArray[0] = mArray[12] = cosine;
            mArray[2] = -sine;
            mArray[10] = sine;
            break;
        // Rotation around the blue color
        case 2:
            mArray[0] = mArray[6] = cosine;
            mArray[1] = sine;
            mArray[5] = -sine;
            break;
        default:
            throw new RuntimeException();
        }
    }

    
Set this colormatrix to the concatenation of the two specified
colormatrices, such that the resulting colormatrix has the same effect
as applying matB and then applying matA.

It is legal for either matA or matB to be the same colormatrix as this.

/**
     * Set this colormatrix to the concatenation of the two specified
     * colormatrices, such that the resulting colormatrix has the same effect
     * as applying matB and then applying matA.
     * <p>
     * It is legal for either matA or matB to be the same colormatrix as this.
     * </p>
     */
    public void setConcat(ColorMatrix matA, ColorMatrix matB) {
        float[] tmp;
        if (matA == this || matB == this) {
            tmp = new float[20];
        } else {
            tmp = mArray;
        }

        final float[] a = matA.mArray;
        final float[] b = matB.mArray;
        int index = 0;
        for (int j = 0; j < 20; j += 5) {
            for (int i = 0; i < 4; i++) {
                tmp[index++] = a[j + 0] * b[i + 0] +  a[j + 1] * b[i + 5] +
                               a[j + 2] * b[i + 10] + a[j + 3] * b[i + 15];
            }
            tmp[index++] = a[j + 0] * b[4] +  a[j + 1] * b[9] +
                           a[j + 2] * b[14] + a[j + 3] * b[19] +
                           a[j + 4];
        }

        if (tmp != mArray) {
            System.arraycopy(tmp, 0, mArray, 0, 20);
        }
    }

    
Concat this colormatrix with the specified prematrix.

This is logically the same as calling setConcat(this, prematrix);

/**
     * Concat this colormatrix with the specified prematrix.
     * <p>
     * This is logically the same as calling setConcat(this, prematrix);
     * </p>
     */
    public void preConcat(ColorMatrix prematrix) {
        setConcat(this, prematrix);
    }

    
Concat this colormatrix with the specified postmatrix.

This is logically the same as calling setConcat(postmatrix, this);

/**
     * Concat this colormatrix with the specified postmatrix.
     * <p>
     * This is logically the same as calling setConcat(postmatrix, this);
     * </p>
     */
    public void postConcat(ColorMatrix postmatrix) {
        setConcat(postmatrix, this);
    }

    ///////////////////////////////////////////////////////////////////////////

    
Set the matrix to affect the saturation of colors.
Params:
sat – A value of 0 maps the color to gray-scale. 1 is identity./**
     * Set the matrix to affect the saturation of colors.
     *
     * @param sat A value of 0 maps the color to gray-scale. 1 is identity.
     */
    public void setSaturation(float sat) {
        reset();
        float[] m = mArray;

        final float invSat = 1 - sat;
        final float R = 0.213f * invSat;
        final float G = 0.715f * invSat;
        final float B = 0.072f * invSat;

        m[0] = R + sat; m[1] = G;       m[2] = B;
        m[5] = R;       m[6] = G + sat; m[7] = B;
        m[10] = R;      m[11] = G;      m[12] = B + sat;
    }

    
Set the matrix to convert RGB to YUV
/**
     * Set the matrix to convert RGB to YUV
     */
    public void setRGB2YUV() {
        reset();
        float[] m = mArray;
        // these coefficients match those in libjpeg
        m[0]  = 0.299f;    m[1]  = 0.587f;    m[2]  = 0.114f;
        m[5]  = -0.16874f; m[6]  = -0.33126f; m[7]  = 0.5f;
        m[10] = 0.5f;      m[11] = -0.41869f; m[12] = -0.08131f;
    }

    
Set the matrix to convert from YUV to RGB
/**
     * Set the matrix to convert from YUV to RGB
     */
    public void setYUV2RGB() {
        reset();
        float[] m = mArray;
        // these coefficients match those in libjpeg
                                        m[2] = 1.402f;
        m[5] = 1;   m[6] = -0.34414f;   m[7] = -0.71414f;
        m[10] = 1;  m[11] = 1.772f;     m[12] = 0;
    }

    @Override
    public boolean equals(Object obj) {
        // if (obj == this) return true; -- NaN value would mean matrix != itself
        if (!(obj instanceof ColorMatrix)) {
            return false;
        }

        // we don't use Arrays.equals(), since that considers NaN == NaN
        final float[] other = ((ColorMatrix) obj).mArray;
        for (int i = 0; i < 20; i++) {
            if (other[i] != mArray[i]) {
                return false;
            }
        }
        return true;
    }
}