BitmapShader 实现圆型图片

我们在写UI的时候经常会碰到要求将一个方形的图片变成一个圆形或者圆角的图片。如果设计师能给一个圆形的图片那当然是最好的。但是有时候为了减少app的大小，往往就一个方形的图片，怎么办能？该如何实现，今天我就来讲讲使用BitmapShader实现圆形图片。

首先获得边框的宽度和颜色

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

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView, defStyle, 0);

        mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH);
        mBorderColor = a.getColor(R.styleable.CircleImageView_border_color, DEFAULT_BORDER_COLOR);

        a.recycle();

        init();
    }

接着在attr.xml文件中配置

然后初始化画笔和着色器

 private void setup() {
        if (mBitmap == null) {
            return;
        }
        //将mBitmap作为着色器，就是在指定区域内绘制mBitmap
        mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
        //将mBitmapPaint图片画笔设置mBitmapShader
        mBitmapPaint.setAntiAlias(true);
        mBitmapPaint.setShader(mBitmapShader);
        //初始化边框画笔mBorderPaint
        mBorderPaint.setStyle(Paint.Style.STROKE);
        mBorderPaint.setAntiAlias(true);
        mBorderPaint.setColor(mBorderColor);
        mBorderPaint.setStrokeWidth(mBorderWidth);
        //获得图片的长宽
        mBitmapHeight = mBitmap.getHeight();
        mBitmapWidth = mBitmap.getWidth();
        //初始化边框矩形
        mBorderRect.set(0, 0, getWidth(), getHeight());
        //获得图片的半径
        mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2, (mBorderRect.width() - mBorderWidth) / 2);
        //初始化绘制矩形
        mDrawableRect.set(mBorderWidth, mBorderWidth, mBorderRect.width() - mBorderWidth, mBorderRect.height() - mBorderWidth);
        mDrawableRadius = Math.min(mDrawableRect.height() / 2, mDrawableRect.width() / 2);

        updateShaderMatrix();
        invalidate();
    }

再更新Shader矩阵

 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;
            //图片放大或者缩小后x轴的偏移
            dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
        } else {
            scale = mDrawableRect.width() / (float) mBitmapWidth;
            //图片放大或者缩小后y轴的偏移
            dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
        }
        // shader的变换矩阵，我们这里主要用于放大或者缩小
        mShaderMatrix.setScale(scale, scale);
        //ShaderMatrix调整坐标轴
        mShaderMatrix.postTranslate((int) (dx + 0.5f) + mBorderWidth, (int) (dy + 0.5f) + mBorderWidth);
        //着色器设置变换矩阵
        mBitmapShader.setLocalMatrix(mShaderMatrix);
    }

偏移量dx、dy的计算，图片放大或者缩小后x轴的偏移,ImageView的坐标原点是在左上角，所以放大或者缩小后右下角已经和边距间距，为了让图片居中移动1/2间距。dy的偏移量也是如此。

最后就是绘制了，在onDraw方法中绘制图片和边框

    @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);
        }
    }

全部代码如下:

package com.jijin.driver.weidgets;

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.ColorFilter;
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;

import com.jijin.driver.R;


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 = 2;

    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 ColorFilter mColorFilter;

    private boolean mReady;
    private boolean mSetupPending;

    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, R.styleable.CircleImageView, defStyle, 0);

        mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH);
        mBorderColor = a.getColor(R.styleable.CircleImageView_border_color, DEFAULT_BORDER_COLOR);

        a.recycle();

        init();
    }

    private void init() {
        super.setScaleType(SCALE_TYPE);
        mReady = true;
        if (mSetupPending) {
            setup();
            mSetupPending = false;
        }
    }

    @Override
    public ScaleType getScaleType() {
        return SCALE_TYPE;
    }

    @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) {
        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 setImageDrawable(Drawable drawable) {
        super.setImageDrawable(drawable);
        mBitmap = getBitmapFromDrawable(drawable);
        setup();
    }
    public Bitmap getImage(){
        return  mBitmap;
    }

    @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();
    }

    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;
        }
        //将mBitmap作为着色器，就是在指定区域内绘制mBitmap
        mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
        //将mBitmapPaint图片画笔设置mBitmapShader
        mBitmapPaint.setAntiAlias(true);
        mBitmapPaint.setShader(mBitmapShader);
        //初始化边框画笔mBorderPaint
        mBorderPaint.setStyle(Paint.Style.STROKE);
        mBorderPaint.setAntiAlias(true);
        mBorderPaint.setColor(mBorderColor);
        mBorderPaint.setStrokeWidth(mBorderWidth);
        //获得图片的长宽
        mBitmapHeight = mBitmap.getHeight();
        mBitmapWidth = mBitmap.getWidth();
        //初始化边框矩形
        mBorderRect.set(0, 0, getWidth(), getHeight());
        //获得图片的半径
        mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2, (mBorderRect.width() - mBorderWidth) / 2);
        //初始化绘制矩形
        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;
        }
        // shader的变换矩阵，我们这里主要用于放大或者缩小
        mShaderMatrix.setScale(scale, scale);

        mShaderMatrix.postTranslate((int) (dx + 0.5f) + mBorderWidth, (int) (dy + 0.5f) + mBorderWidth);
        //着色器设置变换矩阵
        mBitmapShader.setLocalMatrix(mShaderMatrix);
    }

}

BitmapShader 实现圆型图片

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