看了Android版QQ的自定义头像功能，决定自己实现，随便熟悉下android绘制和图片处理这一块的知识。
先看看效果：
思路分析:
这个效果可以用两个View来完成，上层View是一个遮盖物，绘制半透明的颜色，中间挖了一个圆；下层的View用来显示图片，具备移动和缩放的功能，并且能截取某区域内的图片。
涉及到的知识点：
1.Matrix，图片的移动和缩放
2.Paint的setXfermode方法
3.图片放大移动后，截取一部分
编码实现：
自定义三个View:
1.下层View:ClipPhotoView
2.上层遮盖View:ClipPhotoCircleView
3.布局文件:ClipPhotoLayout，实现两层View的布局，且作为整个功能的facade
ClipPhotoCircleView代码:
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); drawMask(canvas); } /** * 绘制蒙版 */ private void drawMask(Canvas canvas) { //画背景颜色 Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888); Canvas c1 = new Canvas(bitmap); c1.drawARGB(150, 0, 0, 0); Paint strokePaint = new Paint(); strokePaint.setAntiAlias(true); strokePaint.setColor(Color.WHITE); strokePaint.setStyle(Paint.Style.STROKE); strokePaint.setStrokeWidth(STROKE_WIDTH); c1.drawCircle(getWidth() / 2, getHeight() / 2, getRadius(), strokePaint); //画圆 Bitmap circleBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888); Canvas c2 = new Canvas(circleBitmap); Paint circlePaint = new Paint(); circlePaint.setStyle(Paint.Style.FILL); circlePaint.setColor(Color.RED); circlePaint.setAntiAlias(true); c2.drawCircle(getWidth() / 2, getHeight() / 2, getRadius(), circlePaint); //两个图层合成 Paint paint = new Paint(); paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT)); c1.drawBitmap(circleBitmap, 0, 0, paint); paint.setXfermode(null); canvas.drawBitmap(bitmap, 0, 0, null); }
使用了setXfermode，Mode为DST_OUT,如下图：
ClipPhotoView代码:
/** * Created by caocong on 10/9/16. * 显示图片的view,可以托动和缩放 */ public class ClipPhotoView extends ImageView implements View.OnTouchListener, ScaleGestureDetector.OnScaleGestureListener { private static final String TAG = ClipPhotoView.class.getSimpleName(); //最大缩放比例 private static final float MAX_SCALE = 4.0f; //最小缩放比例 private static float MIN_SCALE = 1.0f; //matrix array private static final float MATRIX_ARR[] = new float[9]; /** * 状态 */ private static final class Mode { // 初始状态 private static final int NONE = 0; //托动 private static final int DRAG = 1; //缩放 private static final int ZOOM = 2; } //当前状态 private int mMode = Mode.NONE; //缩放手势 private ScaleGestureDetector mScaleDetector; //矩阵 private Matrix mMatrix = new Matrix(); //托动时手指按下的点 private PointF mPrevPointF = new PointF(); //截取的圆框的半径 private int mRadius; //第一次 private boolean firstTime = true; public ClipPhotoView(Context context) { this(context, null); } public ClipPhotoView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public ClipPhotoView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); mScaleDetector = new ScaleGestureDetector(context, this); mRadius = Util.getRadius(getContext()); // 必须设置才能触发 setOnTouchListener(this); setScaleType(ScaleType.MATRIX); } /** * 初始化 */ private void init() { Drawable drawable = getDrawable(); if (drawable == null) { //throw new IllegalArgumentException("drawable can not be null"); return; } initPosAndScale(); } /** * 初始化缩放比例 */ private void initPosAndScale() { if (firstTime) { Drawable drawable = getDrawable(); int width = getWidth(); int height = getHeight(); //初始化 int dw = drawable.getIntrinsicWidth(); int dh = drawable.getIntrinsicHeight(); float scaleX = 1.0f; float scaleY = 1.0f; //是否已经做过缩放处理 boolean isScaled = false; if (width < getDiameter()) { scaleX = getDiameter() * 1.0f / width; isScaled = true; } if (height < getDiameter()) { scaleY = getDiameter() * 1.0f / height; isScaled = true; } float scale = Math.max(scaleX, scaleY); if (isScaled) { MIN_SCALE = scale; } else { MIN_SCALE = Math.max((getDiameter() * 1.0f) / dw, getDiameter() * 1.0f / dh) + 0.01f; } Log.d(TAG, "scale=" + scale); mMatrix.postScale(scale, scale, getWidth() / 2, getHeight() / 2); mMatrix.postTranslate((width - dw) / 2, (height - dh) / 2); setImageMatrix(mMatrix); firstTime = false; } } @Override public boolean onScale(ScaleGestureDetector detector) { float scale = getScale(); float scaleFactor = detector.getScaleFactor(); if ((scale >= MIN_SCALE && scaleFactor > 1.0f) || (scale <= MAX_SCALE && scaleFactor < 1.0f)) { if (scale * scaleFactor <= MIN_SCALE) { scaleFactor = MIN_SCALE / scale; } else if (scale * scaleFactor >= MAX_SCALE) { scaleFactor = MAX_SCALE / scale; } mMatrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(), detector.getFocusY()); checkTrans(); setImageMatrix(mMatrix); } return true; } @Override public boolean onScaleBegin(ScaleGestureDetector detector) { mMode = Mode.ZOOM; return true; } @Override public void onScaleEnd(ScaleGestureDetector detector) { mMode = Mode.NONE; } @Override public boolean onTouch(View v, MotionEvent event) { if (getDrawable() == null) { return false; } mScaleDetector.onTouchEvent(event); switch (event.getAction() & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: mMode = Mode.DRAG; mPrevPointF.set(event.getX(), event.getY()); break; case MotionEvent.ACTION_UP: mMode = Mode.NONE; break; case MotionEvent.ACTION_MOVE: if (mMode == Mode.DRAG && event.getPointerCount() == 1) { float x = event.getX(); float y = event.getY(); float dx = event.getX() - mPrevPointF.x; float dy = event.getY() - mPrevPointF.y; RectF rectF = getMatrixRectF(); // 如果宽度小于屏幕宽度，则禁止左右移动 if (rectF.width() <= getDiameter()) { dx = 0; } // 如果高度小雨屏幕高度，则禁止上下移动 if (rectF.height() <= getDiameter()) { dy = 0; } mMatrix.postTranslate(dx, dy); checkTrans(); //边界判断 setImageMatrix(mMatrix); mPrevPointF.set(x, y); } break; } return true; } /** * 移动边界检查 */ private void checkTrans() { RectF rect = getMatrixRectF(); float deltaX = 0; float deltaY = 0; int width = getWidth(); int height = getHeight(); int horizontalPadding = (width - getDiameter()) / 2; int verticalPadding = (height - getDiameter()) / 2; // 如果宽或高大于屏幕，则控制范围 ; 这里的0.001是因为精度丢失会产生问题 if (rect.width() + 0.01 >= getDiameter()) { if (rect.left > horizontalPadding) { deltaX = -rect.left + horizontalPadding; } if (rect.right < width - horizontalPadding) { deltaX = width - horizontalPadding - rect.right; } } if (rect.height() + 0.01 >= getDiameter()) { if (rect.top > verticalPadding) { deltaY = -rect.top + verticalPadding; } if (rect.bottom < height - verticalPadding) { deltaY = height - verticalPadding - rect.bottom; } } mMatrix.postTranslate(deltaX, deltaY); } /** * 得到直径 */ public int getDiameter() { return mRadius * 2; } /** * 获得缩放值 * * @return */ private float getScale() { return getMatrixValue(Matrix.MSCALE_X); } private float getMatrixValue(int index) { mMatrix.getValues(MATRIX_ARR); return MATRIX_ARR[index]; } /** * 获得Matrix的RectF */ private RectF getMatrixRectF() { Matrix matrix = mMatrix; RectF rect = new RectF(); Drawable d = getDrawable(); if (null != d) { rect.set(0, 0, d.getIntrinsicWidth(), d.getIntrinsicHeight()); matrix.mapRect(rect); } return rect; } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); init(); } /** * 截取图片 * * @return */ Bitmap clip() { Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888); Canvas canvas = new Canvas(bitmap); draw(canvas); int x = (getWidth() - getDiameter()) / 2; int y = (getHeight() - getDiameter()) / 2; return Bitmap.createBitmap(bitmap, x, y, getDiameter(), getDiameter()); } }
缩放和移动使用了Matrix的方法postScale()和postTranslate,要注意控制边界。
截图的代码在clip()方法中，原理：新建一个空白Bitmap,和屏幕一样大的尺寸，然后将当前View绘制的内容复制到到这个Bitmap中，然后截取该Bitmap的一部分。
ClipPhotoLayout代码:
public class ClipPhotoLayout extends FrameLayout { private ClipPhotoCircleView mCircleView; private ClipPhotoView mPhotoView; public ClipPhotoLayout(Context context) { this(context, null); } public ClipPhotoLayout(Context context, AttributeSet attrs) { this(context, attrs, 0); } public ClipPhotoLayout(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(); } private void init() { mCircleView = new ClipPhotoCircleView(getContext()); mPhotoView = new ClipPhotoView(getContext()); android.view.ViewGroup.LayoutParams lp = new LinearLayout.LayoutParams( android.view.ViewGroup.LayoutParams.MATCH_PARENT, android.view.ViewGroup.LayoutParams.MATCH_PARENT); addView(mPhotoView, lp); addView(mCircleView, lp); } public void setImageDrawable(Drawable drawable) { mPhotoView.setImageDrawable(drawable); } public void setImageDrawable(int resId) { setImageDrawable(getContext().getDrawable(resId)); } public Bitmap clipBitmap() { return mPhotoView.clip(); } }
测试MainActivity:
public class MainActivity extends Activity { private ClipPhotoLayout mClipPhotoLayout; private int[] pictures = {R.drawable.mingren, R.drawable.cute, R.drawable.tuxi}; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.scale); setTitle("移动和缩放"); mClipPhotoLayout = (ClipPhotoLayout) findViewById(R.id.clip_layout); mClipPhotoLayout.setImageDrawable(pictures[0]); } public void doClick(View view) { Bitmap bitmap = mClipPhotoLayout.clipBitmap(); Intent intent = new Intent(this, ResultActivity.class); intent.putExtra("photo", bitmap); startActivity(intent); } }
MainActivity的布局文件：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <com.caocong.image.widget.ClipPhotoLayout android:id="@+id/clip_layout" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1.0"/> <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:onClick="doClick" android:text="clip" /> </LinearLayout>
以上所述是小编给大家介绍的Android 仿QQ头像自定义截取功能，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对脚本之家网站的支持！