本例讲解了一个在图片上绘制路径的实例，绘制的路径可以选择普通、浮雕、喷涂三种效果。
效果如下：
下面是实现方法：
public class Main extends Activity implements OnColorChangedListener
{
private MyView myView;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
myView = new MyView(this);
setContentView(myView);
paint = new Paint();
paint.setAntiAlias(true);
paint.setDither(true);
paint.setColor(0xFFFF0000);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setStrokeWidth(6);
emboss = new EmbossMaskFilter(new float[]
{ 1, 1, 1 }, 0.4f, 6, 3.5f);
blur = new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL);
}
private Paint paint;
private MaskFilter emboss;
private MaskFilter blur;
public void colorChanged(int color)
{
paint.setColor(color);
}
public class MyView extends View
{
private Bitmap bitmap1;
private Bitmap bitmap2;
private Canvas canvas;
private Path path;
private Paint bitmapPaint;
//创建一个可在图像上绘制图形的bitmap对象
public void loadBitmap()
{
try
{ //从drawable中装载图像资源，并生成bitmap对象
InputStream is = getResources().openRawResource(
R.drawable.image);
//使用createbitmap创建一个可绘制的bitmap对象，直接装载的不能直接绘制
bitmap2 = BitmapFactory.decodeStream(is);
bitmap1 = Bitmap
.createBitmap(320, 480, Bitmap.Config.ARGB_8888);
//使用bitmap1对象创建一个画布
canvas = new Canvas(bitmap1);
//在bitmap1上绘制2
canvas.drawBitmap(bitmap2, 0, 0, null);
}
catch (Exception e)
{
}
}
public MyView(Context c)
{
super(c);
loadBitmap();
bitmapPaint = new Paint(Paint.DITHER_FLAG);
path = new Path();
}
public void clear()
{
loadBitmap();
invalidate();
}
@Override
protected void onDraw(Canvas canvas)
{
canvas.drawBitmap(bitmap1, 0, 0, bitmapPaint);
canvas.drawPath(path, paint);
}
private float mX, mY;
private void touch_start(float x, float y)
{
path.moveTo(x, y);
mX = x;
mY = y;
}
private void touch_move(float x, float y)
{
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
path.quadTo(mX, mY, x, y);
mX = x;
mY = y;
}
private void touch_up()
{
canvas.drawPath(path, paint);
path.reset();
try
{
FileOutputStream fos = new FileOutputStream("/sdcard/image.png");
bitmap1.compress(CompressFormat.PNG, 100, fos);
fos.close();
}
catch (Exception e)
{
}
}
//捕捉view的触摸事件
@Override
public boolean onTouchEvent(MotionEvent event)
{
float x = event.getX();
float y = event.getY();
switch (event.getAction())
{
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}
}
private final int COLOR_MENU_ID = Menu.FIRST;
private final int EMBOSS_MENU_ID = Menu.FIRST + 1;
private final int BLUR_MENU_ID = Menu.FIRST + 2;
private final int CLEAR_MENU_ID = Menu.FIRST + 3;
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
super.onCreateOptionsMenu(menu);
menu.add(0, COLOR_MENU_ID, 0, "设置颜色");
menu.add(0, EMBOSS_MENU_ID, 0, "浮雕效果");
menu.add(0, BLUR_MENU_ID, 0, "喷涂效果");
menu.add(0, CLEAR_MENU_ID, 0, "清除图形");
return true;
}
@Override
public boolean onPrepareOptionsMenu(Menu menu)
{
super.onPrepareOptionsMenu(menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case COLOR_MENU_ID:
new ColorPickerDialog(this, this, paint.getColor()).show();
return true;
case EMBOSS_MENU_ID:
if (paint.getMaskFilter() != emboss)
{
paint.setMaskFilter(emboss);
}
else
{
paint.setMaskFilter(null);
}
return true;
case BLUR_MENU_ID:
if (paint.getMaskFilter() != blur)
{
paint.setMaskFilter(blur);
}
else
{
paint.setMaskFilter(null);
}
return true;
case CLEAR_MENU_ID:
myView.clear();
return true;
}
return super.onOptionsItemSelected(item);
}
}本例使用的颜色选择器是APIDemo中的一个示例：
public class ColorPickerDialog extends Dialog {
public interface OnColorChangedListener {
void colorChanged(int color);
}
private OnColorChangedListener mListener;
private int mInitialColor;
private static class ColorPickerView extends View {
private Paint mPaint;
private Paint mCenterPaint;
private final int[] mColors;
private OnColorChangedListener mListener;
ColorPickerView(Context c, OnColorChangedListener l, int color) {
super(c);
mListener = l;
mColors = new int[] {
0xFFFF0000, 0xFFFF00FF, 0xFF0000FF, 0xFF00FFFF, 0xFF00FF00,
0xFFFFFF00, 0xFFFF0000
};
Shader s = new SweepGradient(0, 0, mColors, null);
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setShader(s);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(32);
mCenterPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mCenterPaint.setColor(color);
mCenterPaint.setStrokeWidth(5);
}
private boolean mTrackingCenter;
private boolean mHighlightCenter;
@Override
protected void onDraw(Canvas canvas) {
float r = CENTER_X - mPaint.getStrokeWidth()*0.5f;
canvas.translate(CENTER_X, CENTER_X);
canvas.drawOval(new RectF(-r, -r, r, r), mPaint);
canvas.drawCircle(0, 0, CENTER_RADIUS, mCenterPaint);
if (mTrackingCenter) {
int c = mCenterPaint.getColor();
mCenterPaint.setStyle(Paint.Style.STROKE);
if (mHighlightCenter) {
mCenterPaint.setAlpha(0xFF);
} else {
mCenterPaint.setAlpha(0x80);
}
canvas.drawCircle(0, 0,
CENTER_RADIUS + mCenterPaint.getStrokeWidth(),
mCenterPaint);
mCenterPaint.setStyle(Paint.Style.FILL);
mCenterPaint.setColor(c);
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(CENTER_X*2, CENTER_Y*2);
}
private static final int CENTER_X = 100;
private static final int CENTER_Y = 100;
private static final int CENTER_RADIUS = 32;
private int floatToByte(float x) {
int n = java.lang.Math.round(x);
return n;
}
private int pinToByte(int n) {
if (n < 0) {
n = 0;
} else if (n > 255) {
n = 255;
}
return n;
}
private int ave(int s, int d, float p) {
return s + java.lang.Math.round(p * (d - s));
}
private int interpColor(int colors[], float unit) {
if (unit <= 0) {
return colors[0];
}
if (unit >= 1) {
return colors[colors.length - 1];
}
float p = unit * (colors.length - 1);
int i = (int)p;
p -= i;
// now p is just the fractional part [0...1) and i is the index
int c0 = colors[i];
int c1 = colors[i+1];
int a = ave(Color.alpha(c0), Color.alpha(c1), p);
int r = ave(Color.red(c0), Color.red(c1), p);
int g = ave(Color.green(c0), Color.green(c1), p);
int b = ave(Color.blue(c0), Color.blue(c1), p);
return Color.argb(a, r, g, b);
}
private int rotateColor(int color, float rad) {
float deg = rad * 180 / 3.1415927f;
int r = Color.red(color);
int g = Color.green(color);
int b = Color.blue(color);
ColorMatrix cm = new ColorMatrix();
ColorMatrix tmp = new ColorMatrix();
cm.setRGB2YUV();
tmp.setRotate(0, deg);
cm.postConcat(tmp);
tmp.setYUV2RGB();
cm.postConcat(tmp);
final float[] a = cm.getArray();
int ir = floatToByte(a[0] * r + a[1] * g + a[2] * b);
int ig = floatToByte(a[5] * r + a[6] * g + a[7] * b);
int ib = floatToByte(a[10] * r + a[11] * g + a[12] * b);
return Color.argb(Color.alpha(color), pinToByte(ir),
pinToByte(ig), pinToByte(ib));
}
private static final float PI = 3.1415926f;
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX() - CENTER_X;
float y = event.getY() - CENTER_Y;
boolean inCenter = java.lang.Math.sqrt(x*x + y*y) <= CENTER_RADIUS;
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mTrackingCenter = inCenter;
if (inCenter) {
mHighlightCenter = true;
invalidate();
break;
}
case MotionEvent.ACTION_MOVE:
if (mTrackingCenter) {
if (mHighlightCenter != inCenter) {
mHighlightCenter = inCenter;
invalidate();
}
} else {
float angle = (float)java.lang.Math.atan2(y, x);
// need to turn angle [-PI ... PI] into unit [0....1]
float unit = angle/(2*PI);
if (unit < 0) {
unit += 1;
}
mCenterPaint.setColor(interpColor(mColors, unit));
invalidate();
}
break;
case MotionEvent.ACTION_UP:
if (mTrackingCenter) {
if (inCenter) {
mListener.colorChanged(mCenterPaint.getColor());
}
mTrackingCenter = false; // so we draw w/o halo
invalidate();
}
break;
}
return true;
}
}
public ColorPickerDialog(Context context,
OnColorChangedListener listener,
int initialColor) {
super(context);
mListener = listener;
mInitialColor = initialColor;
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
OnColorChangedListener l = new OnColorChangedListener() {
public void colorChanged(int color) {
mListener.colorChanged(color);
dismiss();
}
};
setContentView(new ColorPickerView(getContext(), l, mInitialColor));
setTitle("Pick a Color");
}
}