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ColorMatrix.javaAPI DocAndroid 5.1 API8058Thu Mar 12 22:22:30 GMT 2015android.graphics

ColorMatrix

public class ColorMatrix extends Object
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 ]

Fields Summary
private final float[]
mArray
Constructors Summary
public ColorMatrix()
Create a new colormatrix initialized to identity (as if reset() had been called).


                      
      
        reset();
public ColorMatrix(float[] src)
Create a new colormatrix initialized with the specified array of values.

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

        System.arraycopy(src.mArray, 0, mArray, 0, 20);
Methods Summary
public final float[]getArray()
Return the array of floats representing this colormatrix.

 return mArray;
public voidpostConcat(android.graphics.ColorMatrix postmatrix)
Concat this colormatrix with the specified postmatrix.

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

        setConcat(postmatrix, this);
public voidpreConcat(android.graphics.ColorMatrix prematrix)
Concat this colormatrix with the specified prematrix.

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

        setConcat(this, prematrix);
public voidreset()
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


        final float[] a = mArray;
        Arrays.fill(a, 0);
        a[0] = a[6] = a[12] = a[18] = 1;
public voidset(android.graphics.ColorMatrix src)
Assign the src colormatrix into this matrix, copying all of its values.

        System.arraycopy(src.mArray, 0, mArray, 0, 20);
public voidset(float[] src)
Assign the array of floats into this matrix, copying all of its values.

        System.arraycopy(src, 0, mArray, 0, 20);
public voidsetConcat(android.graphics.ColorMatrix matA, android.graphics.ColorMatrix matB)
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. 

        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);
        }
public voidsetRGB2YUV()
Set the matrix to convert RGB to YUV

        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;
public voidsetRotate(int axis, float degrees)
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 

        reset();
        float radians = degrees * (float)Math.PI / 180;
        float cosine = FloatMath.cos(radians);
        float sine = FloatMath.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();
        }
public voidsetSaturation(float sat)
Set the matrix to affect the saturation of colors.

param
sat A value of 0 maps the color to gray-scale. 1 is identity.

        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;
public voidsetScale(float rScale, float gScale, float bScale, float aScale)
Set this colormatrix to scale by the specified values.

        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;
public voidsetYUV2RGB()
Set the matrix to convert from YUV to RGB

        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;