@Override public void setImageBitmap(Bitmap bm) { super.setImageBitmap(bm); mBitmap = bm; setBitmaps(); } /** * 系統(tǒng)會(huì)調(diào)用這個(gè)方法設(shè)置前景 src */ @Override public void setImageDrawable(Drawable drawable) { super.setImageDrawable(drawable); mBitmap = getBitmapFromDrawable(drawable); setBitmaps(); } @Override public void setImageResource(int resId) { super.setImageResource(resId); mBitmap = getBitmapFromDrawable(getDrawable()); setBitmaps(); } @Override public void setImageURI(Uri uri) { super.setImageURI(uri); mBitmap = getBitmapFromDrawable(getDrawable()); setBitmaps(); }

private void setBitmaps(){ if(null==getBackground()){  throw new IllegalArgumentException(String.format("background is null.")); }else{  backgroundBitmap = getBitmapFromDrawable(getBackground());  invalidate(); } }

@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec,heightMeasureSpec); /**  * 獲得控件的寬高，默認(rèn)MeasureSpec.EXACTLY （ match_parent , accurate ）  * 并且布局文件中應(yīng)該設(shè)置 控件的寬高相等  */ viewWidth = MeasureSpec.getSize(widthMeasureSpec); viewHeight = MeasureSpec.getSize(heightMeasureSpec); }

private Bitmap createImage() { Paint paint = new Paint(); paint.setAntiAlias(true); Bitmap finalBmp = Bitmap.createBitmap(viewWidth,viewHeight, Bitmap.Config.ARGB_8888); /**  * 產(chǎn)生一個(gè)同樣大小的畫布  */ Canvas canvas = new Canvas(finalBmp); /**  * 首先背景圖片  */ canvas.drawBitmap(backgroundBitmap, 0, 0, paint); /**  * 使用SRC_IN，取兩層繪制交集，顯示上層。  */ paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN)); /**  * 繪制前景圖片  */ canvas.drawBitmap(mBitmap, 0, 0, paint); return finalBmp; }

 @Override protected void onDraw(Canvas canvas) { if(mBitmap!=null && backgroundBitmap!=null){  /**  * 對(duì)圖片給進(jìn)行縮放  */  int min = Math.min(viewWidth, viewHeight);  backgroundBitmap = Bitmap.createScaledBitmap(backgroundBitmap, min, min, false);  mBitmap = Bitmap.createScaledBitmap(mBitmap, min, min, false);  /**  * 把最后的bitmap畫上去  */  canvas.drawBitmap(createImage(), 0, 0, null); } }

 /** * Drawable轉(zhuǎn)Bitmap */ private Bitmap getBitmapFromDrawable(Drawable drawable) { super.setScaleType(ScaleType.CENTER_CROP); if (drawable == null) {  return null; } if (drawable instanceof BitmapDrawable) {  return ((BitmapDrawable) drawable).getBitmap(); } try {  Bitmap bitmap;  bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(),Bitmap.Config.ARGB_8888);  Canvas canvas = new Canvas(bitmap);  drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());  drawable.draw(canvas);  return bitmap; } catch (OutOfMemoryError e) {  return null; } }

<cn.fanrunqi.avatarimageview.AvatarImageView  android:layout_width="100dp"  android:layout_height="100dp"  android:background="@drawable/oval_shape"  <!--android:background="@drawable/bg_a"-->  android:src="@drawable/c"  />

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="oval" android:useLevel="false"> <solid android:color="#fff"/> <size android:width="100dp"  android:height="100dp"/></shape>

mBitmapPaint.setShader(mBitmapShader);

canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius, mBitmapPaint);

mBitmapShader.setLocalMatrix(mShaderMatrix);

public class CircleImageView extends ImageView { //縮放類型 private static final ScaleType SCALE_TYPE = ScaleType.CENTER_CROP; private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888; private static final int COLORDRAWABLE_DIMENSION = 2; // 默認(rèn)邊界寬度 private static final int DEFAULT_BORDER_WIDTH = 0; // 默認(rèn)邊界顏色 private static final int DEFAULT_BORDER_COLOR = Color.BLACK; private static final boolean DEFAULT_BORDER_OVERLAY = false; private final RectF mDrawableRect = new RectF(); private final RectF mBorderRect = new RectF(); private final Matrix mShaderMatrix = new Matrix(); //這個(gè)畫筆最重要的是關(guān)聯(lián)了mBitmapShader 使canvas在執(zhí)行的時(shí)候可以切割原圖片(mBitmapShader是關(guān)聯(lián)了原圖的bitmap的) private final Paint mBitmapPaint = new Paint(); //這個(gè)描邊，則與本身的原圖bitmap沒有任何關(guān)聯(lián)， private final Paint mBorderPaint = new Paint(); //這里定義了 圓形邊緣的默認(rèn)寬度和顏色 private int mBorderColor = DEFAULT_BORDER_COLOR; private int mBorderWidth = DEFAULT_BORDER_WIDTH; private Bitmap mBitmap; private BitmapShader mBitmapShader; // 位圖渲染 private int mBitmapWidth; // 位圖寬度 private int mBitmapHeight; // 位圖高度 private float mDrawableRadius;// 圖片半徑 private float mBorderRadius;// 帶邊框的的圖片半徑 private ColorFilter mColorFilter; //初始false private boolean mReady; private boolean mSetupPending; private boolean mBorderOverlay; //構(gòu)造函數(shù) public CircleImageView(Context context) { super(context); init(); } //構(gòu)造函數(shù) public CircleImageView(Context context, AttributeSet attrs) { this(context, attrs, 0); } /** * 構(gòu)造函數(shù) */ public CircleImageView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView, defStyle, 0); //通過TypedArray提供的一系列方法getXXXX取得我們?cè)趚ml里定義的參數(shù)值； // 獲取邊界的寬度 mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH); // 獲取邊界的顏色 mBorderColor = a.getColor(R.styleable.CircleImageView_border_color, DEFAULT_BORDER_COLOR); mBorderOverlay = a.getBoolean(R.styleable.CircleImageView_border_overlay, DEFAULT_BORDER_OVERLAY); //調(diào)用 recycle() 回收TypedArray,以便后面重用 a.recycle(); init(); } /** * 作用就是保證第一次執(zhí)行setup函數(shù)里下面代碼要在構(gòu)造函數(shù)執(zhí)行完畢時(shí)調(diào)用 */ private void init() { //在這里ScaleType被強(qiáng)制設(shè)定為CENTER_CROP，就是將圖片水平垂直居中，進(jìn)行縮放。 super.setScaleType(SCALE_TYPE); mReady = true; if (mSetupPending) {  setup();  mSetupPending = false; } } @Override public ScaleType getScaleType() { return SCALE_TYPE; } /** * 這里明確指出 此種imageview 只支持CENTER_CROP 這一種屬性 * * @param scaleType */ @Override public void setScaleType(ScaleType scaleType) { if (scaleType != SCALE_TYPE) {  throw new IllegalArgumentException(String.format("ScaleType %s not supported.", scaleType)); } } @Override public void setAdjustViewBounds(boolean adjustViewBounds) { if (adjustViewBounds) {  throw new IllegalArgumentException("adjustViewBounds not supported."); } } @Override protected void onDraw(Canvas canvas) { //如果圖片不存在就不畫 if (getDrawable() == null) {  return; } //繪制內(nèi)圓形 圖片 畫筆為mBitmapPaint canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius, mBitmapPaint); //如果圓形邊緣的寬度不為0 我們還要繪制帶邊界的外圓形 邊界畫筆為mBorderPaint if (mBorderWidth != 0) {  canvas.drawCircle(getWidth() / 2, getHeight() / 2, mBorderRadius, mBorderPaint); } } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); setup(); } public int getBorderColor() { return mBorderColor; } public void setBorderColor(int borderColor) { if (borderColor == mBorderColor) {  return; } mBorderColor = borderColor; mBorderPaint.setColor(mBorderColor); invalidate(); } public void setBorderColorResource( int borderColorRes) { setBorderColor(getContext().getResources().getColor(borderColorRes)); } public int getBorderWidth() { return mBorderWidth; } public void setBorderWidth(int borderWidth) { if (borderWidth == mBorderWidth) {  return; } mBorderWidth = borderWidth; setup(); } public boolean isBorderOverlay() { return mBorderOverlay; } public void setBorderOverlay(boolean borderOverlay) { if (borderOverlay == mBorderOverlay) {  return; } mBorderOverlay = borderOverlay; setup(); } /** * 以下四個(gè)函數(shù)都是 * 復(fù)寫ImageView的setImageXxx()方法 * 注意這個(gè)函數(shù)先于構(gòu)造函數(shù)調(diào)用之前調(diào)用 * @param bm */ @Override public void setImageBitmap(Bitmap bm) { super.setImageBitmap(bm); mBitmap = bm; setup(); } @Override public void setImageDrawable(Drawable drawable) { super.setImageDrawable(drawable); mBitmap = getBitmapFromDrawable(drawable); setup(); } @Override public void setImageResource( int resId) { super.setImageResource(resId); mBitmap = getBitmapFromDrawable(getDrawable()); setup(); } @Override public void setImageURI(Uri uri) { super.setImageURI(uri); mBitmap = getBitmapFromDrawable(getDrawable()); setup(); } @Override public void setColorFilter(ColorFilter cf) { if (cf == mColorFilter) {  return; } mColorFilter = cf; mBitmapPaint.setColorFilter(mColorFilter); invalidate(); } /** * Drawable轉(zhuǎn)Bitmap * @param drawable * @return */ private Bitmap getBitmapFromDrawable(Drawable drawable) { if (drawable == null) {  return null; } if (drawable instanceof BitmapDrawable) {  //通常來說 我們的代碼就是執(zhí)行到這里就返回了。返回的就是我們最原始的bitmap  return ((BitmapDrawable) drawable).getBitmap(); } try {  Bitmap bitmap;  if (drawable instanceof ColorDrawable) {  bitmap = Bitmap.createBitmap(COLORDRAWABLE_DIMENSION, COLORDRAWABLE_DIMENSION, BITMAP_CONFIG);  } else {  bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), BITMAP_CONFIG);  }  Canvas canvas = new Canvas(bitmap);  drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());  drawable.draw(canvas);  return bitmap; } catch (OutOfMemoryError e) {  return null; } } /** * 這個(gè)函數(shù)很關(guān)鍵，進(jìn)行圖片畫筆邊界畫筆(Paint)一些重繪參數(shù)初始化： * 構(gòu)建渲染器BitmapShader用Bitmap來填充繪制區(qū)域,設(shè)置樣式以及內(nèi)外圓半徑計(jì)算等， * 以及調(diào)用updateShaderMatrix()函數(shù)和 invalidate()函數(shù)； */ private void setup() { //因?yàn)閙Ready默認(rèn)值為false,所以第一次進(jìn)這個(gè)函數(shù)的時(shí)候if語句為真進(jìn)入括號(hào)體內(nèi) //設(shè)置mSetupPending為true然后直接返回，后面的代碼并沒有執(zhí)行。 if (!mReady) {  mSetupPending = true;  return; } //防止空指針異常 if (mBitmap == null) {  return; } // 構(gòu)建渲染器，用mBitmap位圖來填充繪制區(qū)域,參數(shù)值代表如果圖片太小的話 就直接拉伸 mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP); // 設(shè)置圖片畫筆反鋸齒 mBitmapPaint.setAntiAlias(true); // 設(shè)置圖片畫筆渲染器 mBitmapPaint.setShader(mBitmapShader); // 設(shè)置邊界畫筆樣式 mBorderPaint.setStyle(Paint.Style.STROKE);//設(shè)畫筆為空心 mBorderPaint.setAntiAlias(true); mBorderPaint.setColor(mBorderColor); //畫筆顏色 mBorderPaint.setStrokeWidth(mBorderWidth);//畫筆邊界寬度 //這個(gè)地方是取的原圖片的寬高 mBitmapHeight = mBitmap.getHeight(); mBitmapWidth = mBitmap.getWidth(); // 設(shè)置含邊界顯示區(qū)域，取的是CircleImageView的布局實(shí)際大小，為方形 mBorderRect.set(0, 0, getWidth(), getHeight()); //計(jì)算 圓形帶邊界部分（外圓）的最小半徑，取mBorderRect的寬高減去一個(gè)邊緣大小的一半的較小值 mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2, (mBorderRect.width() - mBorderWidth) / 2); // 初始圖片顯示區(qū)域?yàn)閙BorderRect（CircleImageView的布局實(shí)際大小） mDrawableRect.set(mBorderRect); if (!mBorderOverlay) {  //demo里始終執(zhí)行  //通過inset方法 使得圖片顯示的區(qū)域從mBorderRect大小上下左右內(nèi)移邊界的寬度形成區(qū)域  mDrawableRect.inset(mBorderWidth, mBorderWidth); } //這里計(jì)算的是內(nèi)圓的最小半徑，也即去除邊界寬度的半徑 mDrawableRadius = Math.min(mDrawableRect.height() / 2, mDrawableRect.width() / 2); //設(shè)置渲染器的變換矩陣也即是mBitmap用何種縮放形式填充 updateShaderMatrix(); //手動(dòng)觸發(fā)ondraw()函數(shù) 完成最終的繪制 invalidate(); } /** * 這個(gè)函數(shù)為設(shè)置BitmapShader的Matrix參數(shù)，設(shè)置最小縮放比例，平移參數(shù)。 * 作用：保證圖片損失度最小和始終繪制圖片正中央的那部分 */ private void updateShaderMatrix() { float scale; float dx = 0; float dy = 0; mShaderMatrix.set(null); // 這里不好理解 這個(gè)不等式也就是(mBitmapWidth / mDrawableRect.width()) > (mBitmapHeight / mDrawableRect.height()) //取最小的縮放比例 if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width() * mBitmapHeight) {  //y軸縮放 x軸平移 使得圖片的y軸方向的邊的尺寸縮放到圖片顯示區(qū)域（mDrawableRect）一樣）  scale = mDrawableRect.height() / (float) mBitmapHeight;  dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f; } else {  //x軸縮放 y軸平移 使得圖片的x軸方向的邊的尺寸縮放到圖片顯示區(qū)域（mDrawableRect）一樣）  scale = mDrawableRect.width() / (float) mBitmapWidth;  dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f; } // shaeder的變換矩陣，我們這里主要用于放大或者縮小。 mShaderMatrix.setScale(scale, scale); // 平移 mShaderMatrix.postTranslate((int) (dx + 0.5f) + mDrawableRect.left, (int) (dy + 0.5f) + mDrawableRect.top); // 設(shè)置變換矩陣 mBitmapShader.setLocalMatrix(mShaderMatrix); }}

Path path = new Path(); 

@Overrideprotected void onDraw(Canvas canvas) { Path path = new Path();  //按照逆時(shí)針方向添加一個(gè)圓 path.addCircle(float x, float y, mRadius, Direction.CCW); //先將canvas保存 canvas.save(); //把canvas修剪成指定的路徑區(qū)域 canvas.clipPath(path); //繪制圖形Bitmap canvas.drawBitmap(Bitmap,float left, float top, mPaint); //恢復(fù)Canvas canvas.restore();}