android 繪制圓形圖片

1.自定義CircleImageView，加載即可使用

    import android.content.Context;

    import android.content.res.TypedArray;

    import android.graphics.Bitmap;

    import android.graphics.BitmapShader;

    import android.graphics.Canvas;

    import android.graphics.Color;

    import android.graphics.Matrix;

    import android.graphics.Paint;

    import android.graphics.RectF;

    import android.graphics.Shader;

    import android.graphics.drawable.BitmapDrawable;

    import android.graphics.drawable.ColorDrawable;

    import android.graphics.drawable.Drawable;

    import android.net.Uri;

    import android.util.AttributeSet;

    import android.widget.ImageView;


public class CircleImageView extends ImageView {  

    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 = 1;  

    private static final int DEFAULT_BORDER_WIDTH = 0;  
    private static final int DEFAULT_BORDER_COLOR = Color.BLACK;  

    private final RectF mDrawableRect = new RectF();  
    private final RectF mBorderRect = new RectF();  

    private final Matrix mShaderMatrix = new Matrix();  
    private final Paint mBitmapPaint = new Paint();  
    private final Paint mBorderPaint = new Paint();  

    private int mBorderColor = DEFAULT_BORDER_COLOR;  
    private int mBorderWidth = DEFAULT_BORDER_WIDTH;  

    private Bitmap mBitmap;  
    private BitmapShader mBitmapShader;  
    private int mBitmapWidth;  
    private int mBitmapHeight;  

    private float mDrawableRadius;  
    private float mBorderRadius;  

    private boolean mReady;  
    private boolean mSetupPending;  

    public static final int CircleImageView_border_width = 0;  
    public static final int CircleImageView_border_color = 1;  
    public static final int[] CircleImageView = { 0x7f010000, 0x7f010001 };  

    public CircleImageView(Context context) {  
        super(context);  
        init();  
    }  

    public CircleImageView(Context context, AttributeSet attrs) {  
        this(context, attrs, 0);  
    }  

    public CircleImageView(Context context, AttributeSet attrs, int defStyle) {  
        super(context, attrs, defStyle);  

        TypedArray a = context.obtainStyledAttributes(attrs, CircleImageView,defStyle, 0);  
        mBorderWidth = a.getDimensionPixelSize(0, DEFAULT_BORDER_WIDTH);  
        mBorderColor = a.getColor(CircleImageView_border_color,DEFAULT_BORDER_COLOR);  
        a.recycle();  
        init();  
    }  

    private void init() {  
        super.setScaleType(SCALE_TYPE);  
        mReady = true;  

        if (mSetupPending) {  
            setup();  
            mSetupPending = false;  
        }  
    }  

    @Override  
    protected void onDraw(Canvas canvas) {  
        if (getDrawable() == null) {  
            return;  
        }  
        canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius,  
                mBitmapPaint);  
        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 int getBorderWidth() {  
        return mBorderWidth;  
    }  

    public void setBorderWidth(int borderWidth) {  
        if (borderWidth == mBorderWidth) {  
            return;  
        }  
        mBorderWidth = borderWidth;  
        setup();  
    }  

    @Override  
    public void setImageBitmap(Bitmap bm) {  
        super.setImageBitmap(bm);  
        mBitmap = bm;  
        setup();  
    }  

    @Override  
    public void setBackgroundResource(int resid) {  
        super.setBackgroundResource(resid);  
        mBitmap = getBitmapFromDrawable(getDrawable());  
        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();  
    }  

    private Bitmap getBitmapFromDrawable(Drawable drawable) {  
        if (drawable == null) {  
            return null;  
        }  

        if (drawable instanceof BitmapDrawable) {  
            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;  
        }  
    }  

    private void setup() {  
        if (!mReady) {  
            mSetupPending = true;  
            return;  
        }  

        if (mBitmap == null) {  
            return;  
        }  

        mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP,  
                Shader.TileMode.CLAMP);  

        mBitmapPaint.setAntiAlias(true);  
        mBitmapPaint.setShader(mBitmapShader);  

        mBorderPaint.setStyle(Paint.Style.STROKE);  
        mBorderPaint.setAntiAlias(true);  
        mBorderPaint.setColor(mBorderColor);  
        mBorderPaint.setStrokeWidth(mBorderWidth);  

        mBitmapHeight = mBitmap.getHeight();  
        mBitmapWidth = mBitmap.getWidth();  

        mBorderRect.set(0, 0, getWidth(), getHeight());  
        mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2,  
                (mBorderRect.width() - mBorderWidth) / 2);  

        mDrawableRect.set(mBorderWidth, mBorderWidth, mBorderRect.width()  
                - mBorderWidth, mBorderRect.height() - mBorderWidth);  
        mDrawableRadius = Math.min(mDrawableRect.height() / 2,  
                mDrawableRect.width() / 2);  

        updateShaderMatrix();  
        invalidate();  
    }  

    private void updateShaderMatrix() {  
        float scale;  
        float dx = 0;  
        float dy = 0;  

        mShaderMatrix.set(null);  

        if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width()  
                * mBitmapHeight) {  
            scale = mDrawableRect.height() / (float) mBitmapHeight;  
            dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;  
        } else {  
            scale = mDrawableRect.width() / (float) mBitmapWidth;  
            dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;  
        }  

        mShaderMatrix.setScale(scale, scale);  
        mShaderMatrix.postTranslate((int) (dx + 0.5f) + mBorderWidth,  
                (int) (dy + 0.5f) + mBorderWidth);  

        mBitmapShader.setLocalMatrix(mShaderMatrix);  
    }  
}  </pre> 



 2.繪制現有圖片 

private Bitmap cicleImage(int id) {

        // 加載現有圖片

        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), id);

        int width = bitmap.getWidth();

        int height = bitmap.getHeight();


    // 構造新圖紙  
    Bitmap output = Bitmap.createBitmap(width, height,  
            Bitmap.Config.ARGB_8888);  
    Canvas canvas = new Canvas(output);  

    Paint paint = new Paint();  
    paint.setAntiAlias(true); // 抗鋸齒  
    canvas.drawARGB(0, 0, 0, 0); // 將背景繪制成黑色  

    // 畫一個灰色的實心園  
    paint.setColor(0xff424242);  
    canvas.drawCircle(width / 2, height / 2, width / 2, paint);  

    /* [Sa * Da, Sc * Da] */  
    // 取兩層繪制交集，顯示上層，本例下層是剛繪制的實心園，上層是即將繪制  
    // 的圖片，兩者的交集就是個園，顯示上層，就把圖片中的園形部分顯示出來了  
    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));  

    // 繪制現有圖片  
    Rect src = new Rect(0, 0, width, width);  
    Rect dst = new Rect(0, 0, width, height);  
    //Rect src: 是對圖片進行裁截，若是空null則顯示整個圖片  
    //Rect dst：是圖片在Canvas畫布中顯示的區域，大于src則把src的裁截區放大， 小于src則把src的裁截區縮小。  
    canvas.drawBitmap(bitmap, src, dst, paint);  
    return output;  
}  </pre>