Android Paint之ColorFilter详解

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在之前讲到Android Paint的使用详解的时候，其中setColorFilter(ColorFilter filter)方法没有讲，今天就来简单的分析一下，在Android中ColorFilter共有3个子类，ColorMatrixColorFilter，LightingColorFilter，PorterDuffColorFilter，今天先来看第一个ColorMatrixColorFilter，ColorMatrixColorFilter的构造方法很简单，一个是传入数组，一个是传入ColorMatrix类型的对象

public ColorMatrixColorFilter(ColorMatrix matrix) {
mMatrix.set(matrix);
update();
}

public ColorMatrixColorFilter(float[] array) {
if (array.length < 20) {
throw new ArrayIndexOutOfBoundsException();
}
mMatrix.set(array);
update();
}

这里主要来看一下ColorMatrix这个类，它内部有一个数组mArray，其实他保存的是一个4x5颜色矩阵，

*  [ a, b, c, d, e,
*    f, g, h, i, j,
*    k, l, m, n, o,
*    p, q, r, s, t ]

可以用来修改ARGB的值，其中 第一行决定红色R，第二行决定绿色G，第三行决定蓝色B，第四行决定了透明度A，第五列是颜色的偏移量
而图像的ARGB值存储在一个5*1的颜色分量矩阵中[R, G, B, A,1]。最终运算的结果是两矩阵相乘

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;

我们看到mArray的大小为20，也就相当于一个4*5的数组，

private final float[] mArray = new float[20];

在初始化的时候，矩阵的数值会进行初始化

/**
* 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;
}

其中第五列是偏移量，比如

[ 1 0 0 0 8
0 1 0 0 8
0 0 1 0 8
0 0 0 1 0 ]

表示个颜色分量计算完成之后要在加上8，其中最后一行是表示透明度的，一般不要修改。我们来演示一下public class ColorFilterView extends View {
private Paint mPaint;
private Bitmap mBitmap;
private int padding = 12;
float[] colorMatrix = {
1, 0, 0, 0, 0, //red
0, 0, 0, 0, 0, //green
0, 0, 0, 0, 0, //blue
0, 0, 0, 1, 0 //alpha
};
private ColorMatrixColorFilter mLightingColorFilter= new ColorMatrixColorFilter(colorMatrix);

public ColorFilterView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}

private void init() {
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (int i = 0; i < 8; i++) {
mPaint.setColorFilter(mLightingColorFilter);
canvas.drawBitmap(mBitmap,
(i % 4) * (mBitmap.getWidth() + padding), (i / 4)
* (mBitmap.getHeight() + padding), mPaint);
}
}

}看一下结果



再来修改一下 float[] colorMatrix = {
1, 0, 0, 0, 0, //red
0, 1, 0, 0, 0, //green
0, 0, 0, 0, 0, //blue
0, 0, 0, 1, 0 //alpha
};看一下运行结果



最后在修改一下，让他还原正常图片 float[] colorMatrix = {
1, 0, 0, 0, 0, //red
0, 1, 0, 0, 0, //green
0, 0, 1, 0, 0, //blue
0, 0, 0, 1, 0 //alpha
};看一下结果



OK，上面的演示完了，我们看下面的一个矩阵。

[ 1 0 0 0 8
0 2 0 0 8
0 0 3 0 8
0 0 0 1 0 ]

他表示红色分量偏移8，绿色分量*2在偏移8，蓝色分量*3在偏移8。下面看一下主要的方法，setScale(float rScale, float gScale, float bScale, float aScale)

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;
}

这个和矩阵刚初始化的时候差不多，不过这里的值不是1，是我们传入的值，代表的是亮度，我们看一下

public class ColorFilterView extends View {
private Paint mPaint;
private Bitmap mBitmap;
private ColorMatrix colorMatrix = new ColorMatrix();
private ColorMatrixColorFilter matrixColorFilter[] = new ColorMatrixColorFilter[24];
private int padding = 12;

public ColorFilterView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}

private void init() {
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
for (int i = 0; i < 24; i++) {
if (i < 8)
colorMatrix.setScale(i * .1f, i * .1f, i * .1f, i * .1f);
else if (i < 16)
colorMatrix.setScale(i * .1f, i * .1f, i * .1f, i * .1f);
else
colorMatrix.setScale(i * .1f, i * .1f, i * .1f, i * .1f);
matrixColorFilter[i] = new ColorMatrixColorFilter(colorMatrix);
}
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (int i = 0; i < 24; i++) {
mPaint.setColorFilter(matrixColorFilter[i]);
canvas.drawBitmap(mBitmap,
(i % 4) * (mBitmap.getWidth() + padding), (i / 4)
* (mBitmap.getHeight() + padding), mPaint);
}
}
}

我们看一下运行结果



再来修改一下

for (int i = 0; i < 24; i++) {
if (i < 8)
colorMatrix.setScale(i * .1f, i * .3f, i * .9f, i * .1f);
else if (i < 16)
colorMatrix.setScale(i * .1f, i * .3f, i * .9f, i * .1f);
else
colorMatrix.setScale(i * .1f, i * .3f, i * .9f, i * .1f);
matrixColorFilter[i] = new ColorMatrixColorFilter(colorMatrix);
}

看一下运行结果



再看另一个方法setRotate(int axis, float degrees)，表示的是色相

/**
* 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();
}
}

其中axis为0时表示的是红色分量旋转的角度，为1时是绿色分量旋转的角度，为2时是蓝色分量旋转的角度，

for (int i = 0; i < 24; i++) {
if (i < 8)
colorMatrix.setRotate(0, i*50);
else if (i < 16)
colorMatrix.setRotate(1, i*50);
else
colorMatrix.setRotate(2, i*50);
matrixColorFilter[i] = new ColorMatrixColorFilter(colorMatrix);
}

看一下运行结果



再来修改一下

for (int i = 0; i < 24; i++) {
if (i < 8)
colorMatrix.setRotate(0, i*50);
else if (i < 16)
colorMatrix.setRotate(1, (i%8)*50);
else
colorMatrix.setRotate(2, (i%8)*50);
matrixColorFilter[i] = new ColorMatrixColorFilter(colorMatrix);
}

看一下运行结果



再看另一个方法setSaturation(float sat)，代表的是饱和度，其中0是灰色，1是正常 for (int i = 0; i < 24; i++) {
if (i < 8)
colorMatrix.setSaturation(i*.2f);
else if (i < 16)
colorMatrix.setSaturation(i*.5f);
else
colorMatrix.setSaturation(i*2f);
matrixColorFilter[i] = new ColorMatrixColorFilter(colorMatrix);
}运行结果为



setConcat(ColorMatrix matA, ColorMatrix matB)，两矩阵相乘 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);
}
}preConcat(ColorMatrix prematrix)前乘，postConcat(ColorMatrix postmatrix)后乘，调用的都是setConcat(ColorMatrix matA, ColorMatrix matB)方法，因为矩阵的乘法不具有交换律，改变两个矩阵的位置会产生不同的结果。
再来看ColorFilter的另一个子类LightingColorFilter光线颜色过滤，就一个构造方法 public LightingColorFilter(int mul, int add) {
mMul = mul;
mAdd = add;
update();
}mul表示颜色增加的倍数，add为色彩增加，

public class ColorFilterView extends View {
private Paint mPaint;
private Bitmap mBitmap;
private LightingColorFilter mLightingColorFilter[] = new LightingColorFilter[8];
private int padding = 12;

public ColorFilterView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}

private void init() {
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
//不变
mLightingColorFilter[0] = new LightingColorFilter(0xFFFFFFFF,
0x00000000);
//去掉红色
mLightingColorFilter[1] = new LightingColorFilter(0xFF00FFFF,
0x00000000);
//去掉绿色
mLightingColorFilter[3] = new LightingColorFilter(0xFFFF00FF,
0x00000000);
//去掉蓝色
mLightingColorFilter[4] = new LightingColorFilter(0xFFFFFF00,
0x00000000);
//增加红色
mLightingColorFilter[5] = new LightingColorFilter(0xFFFFFFFF,
0x00560000);
//增加绿色
mLightingColorFilter[6] = new LightingColorFilter(0xFFFFFFFF,
0x00006400);
//增加蓝色
mLightingColorFilter[7] = new LightingColorFilter(0xFFFFFFFF,
0x00000056);
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (int i = 0; i < 8; i++) {
mPaint.setColorFilter(mLightingColorFilter[i]);
canvas.drawBitmap(mBitmap,
(i % 4) * (mBitmap.getWidth() + padding), (i / 4)
* (mBitmap.getHeight() + padding), mPaint);
}
}

}

运行结果为



再来看ColorFilter的最后一个子类PorterDuffColorFilter，他也是只有一个构造方法 /**
* Create a color filter that uses the specified color and Porter-Duff mode.
*
* @param color The ARGB source color used with the specified Porter-Duff mode
* @param mode The porter-duff mode that is applied
*
* @see Color
* @see #setColor(int)
* @see #setMode(android.graphics.PorterDuff.Mode)
*/
public PorterDuffColorFilter(@ColorInt int color, @NonNull PorterDuff.Mode mode) {
mColor = color;
mMode = mode;
update();
}我们看一下

public class ColorFilterView extends View {
private Paint mPaint;
private Bitmap mBitmap;
private int length = PorterDuff.Mode.values().length;
private PorterDuffColorFilter mLightingColorFilter[] = new PorterDuffColorFilter[length];
private int padding = 12;

public ColorFilterView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}

private void init() {
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
int i = 0;
for (PorterDuff.Mode e : PorterDuff.Mode.values())
mLightingColorFilter[i++] = new PorterDuffColorFilter(Color.YELLOW,
e);
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (int i = 0; i < length; i++) {
mPaint.setColorFilter(mLightingColorFilter[i]);
canvas.drawBitmap(mBitmap,
(i % 4) * (mBitmap.getWidth() + padding), (i / 4)
* (mBitmap.getHeight() + padding), mPaint);
}
}

}

运行结果为



其中Mode是之前在讲到Android Paint的使用详解的时候讲到的18种混合模式，OK，到此为止，已经分析完毕。