图片的二次采样,将已有的图片转为圆角或者圆形图片

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Shader.TileMode;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.util.TypedValue;
import android.widget.ImageView;

import com.cfldcn.housing.R;
public class RoundImageView extends ImageView {
 /**
  * 图片的类型,圆形or圆角
  */
 private int type;
 public static final int TYPE_CIRCLE = 0;
 public static final int TYPE_ROUND = 1;
 /**
  * 圆角大小的默认值
  */
 private static final int BODER_RADIUS_DEFAULT = 10;
 /**
  * 圆角的大小
  */
 private int mBorderRadius;

 /**
  * 绘图的Paint
  */
 private Paint mBitmapPaint;
 /**
  * 圆角的半径
  */
 private int mRadius;
 /**
  * 3x3 矩阵,主要用于缩小放大
  */
 private Matrix mMatrix;
 /**
  * 渲染图像,使用图像为绘制图形着色
  */
 private BitmapShader mBitmapShader;
 /**
  * view的宽度
  */
 private int mWidth;
 private RectF mRoundRect;

 public RoundImageView(Context context, AttributeSet attrs) {

  super(context, attrs);
  mMatrix = new Matrix();
  mBitmapPaint = new Paint();
  mBitmapPaint.setAntiAlias(true);

  TypedArray a = context.obtainStyledAttributes(attrs,
    R.styleable.RoundImageView);

  mBorderRadius = a.getDimensionPixelSize(
    R.styleable.RoundImageView_borderRadius, (int) TypedValue
      .applyDimension(TypedValue.COMPLEX_UNIT_DIP,
        BODER_RADIUS_DEFAULT, getResources()
          .getDisplayMetrics()));// 默认为10dp
  type = a.getInt(R.styleable.RoundImageView_type, TYPE_CIRCLE);// 默认为Circle

  a.recycle();
 }

 public RoundImageView(Context context) {
  this(context, null);
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);

  /**
   * 如果类型是圆形,则强制改变view的宽高一致,以小值为准
   */
  if (type == TYPE_CIRCLE) {
   mWidth = Math.min(getMeasuredWidth(), getMeasuredHeight());
   mRadius = mWidth / 2;
   setMeasuredDimension(mWidth, mWidth);
  }

 }

 /**
  * 初始化BitmapShader
  */
 private void setUpShader() {
  Drawable drawable = getDrawable();
  if (drawable == null) {
   return;
  }

  Bitmap bmp = drawableToBitamp(drawable);
  // 将bmp作为着色器,就是在指定区域内绘制bmp
  mBitmapShader = new BitmapShader(bmp, TileMode.CLAMP, TileMode.CLAMP);
  float scale = 1.0f;
  if (type == TYPE_CIRCLE) {
   // 拿到bitmap宽或高的小值
   int bSize = Math.min(bmp.getWidth(), bmp.getHeight());
   scale = mWidth * 1.0f / bSize;

  } else if (type == TYPE_ROUND) {
   Log.e("TAG",
     "b'w = " + bmp.getWidth() + " , " + "b'h = "
       + bmp.getHeight());
   if (!(bmp.getWidth() == getWidth() && bmp.getHeight() == getHeight())) {
    // 如果图片的宽或者高与view的宽高不匹配,计算出需要缩放的比例;缩放后的图片的宽高,一定要大于我们view的宽高;所以我们这里取大值;
    scale = Math.max(getWidth() * 1.0f / bmp.getWidth(),
      getHeight() * 1.0f / bmp.getHeight());
   }

  }
  // shader的变换矩阵,我们这里主要用于放大或者缩小
  mMatrix.setScale(scale, scale);
  // 设置变换矩阵
  mBitmapShader.setLocalMatrix(mMatrix);
  // 设置shader
  mBitmapPaint.setShader(mBitmapShader);
 }

 @Override
 protected void onDraw(Canvas canvas) {
  Log.e("TAG", "onDraw");
  if (getDrawable() == null) {
   return;
  }
  setUpShader();

  if (type == TYPE_ROUND) {
   canvas.drawRoundRect(mRoundRect, mBorderRadius, mBorderRadius,
     mBitmapPaint);
  } else {
   canvas.drawCircle(mRadius, mRadius, mRadius, mBitmapPaint);
   // drawSomeThing(canvas);
  }
 }

 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);

  // 圆角图片的范围
  if (type == TYPE_ROUND)
   mRoundRect = new RectF(0, 0, w, h);
 }

 /**
  * drawable转bitmap
  * 
  * @param drawable
  * @return
  */
 private Bitmap drawableToBitamp(Drawable drawable) {
  if (drawable instanceof BitmapDrawable) {
   BitmapDrawable bd = (BitmapDrawable) drawable;
   return bd.getBitmap();
  }
  int w = drawable.getIntrinsicWidth();
  int h = drawable.getIntrinsicHeight();
  Bitmap bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
  Canvas canvas = new Canvas(bitmap);
  drawable.setBounds(0, 0, w, h);
  drawable.draw(canvas);
  return bitmap;
 }

 private static final String STATE_INSTANCE = "state_instance";
 private static final String STATE_TYPE = "state_type";
 private static final String STATE_BORDER_RADIUS = "state_border_radius";

 @Override
 protected Parcelable onSaveInstanceState() {
  Bundle bundle = new Bundle();
  bundle.putParcelable(STATE_INSTANCE, super.onSaveInstanceState());
  bundle.putInt(STATE_TYPE, type);
  bundle.putInt(STATE_BORDER_RADIUS, mBorderRadius);
  return bundle;
 }

 @Override
 protected void onRestoreInstanceState(Parcelable state) {
  if (state instanceof Bundle) {
   Bundle bundle = (Bundle) state;
   super.onRestoreInstanceState(((Bundle) state)
     .getParcelable(STATE_INSTANCE));
   this.type = bundle.getInt(STATE_TYPE);
   this.mBorderRadius = bundle.getInt(STATE_BORDER_RADIUS);
  } else {
   super.onRestoreInstanceState(state);
  }

 }

 public void setBorderRadius(int borderRadius) {
  int pxVal = dp2px(borderRadius);
  if (this.mBorderRadius != pxVal) {
   this.mBorderRadius = pxVal;
   invalidate();
  }
 }

 public void setType(int type) {
  if (this.type != type) {
   this.type = type;
   if (this.type != TYPE_ROUND && this.type != TYPE_CIRCLE) {
    this.type = TYPE_CIRCLE;
   }
   requestLayout();
  }

 }

 public int dp2px(int dpVal) {
  return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
    dpVal, getResources().getDisplayMetrics());
 }

}

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