android 通过修改图片像素实现CircleImageView

CircleImageView实现方法有很多种，各有优缺点，因此需要按照不同的场景使用。我们今天使用修改图片像素的方法实现CircleImageView，主要知识点无非是勾股定理和点到圆形的距离。

素材图片：

效果如下：

1、clipPath裁剪画布

该方法支持的最小版本是Android 4.3(API Level 18)，方便快捷，但是不支持硬件加，此外也存在Path既有的缺点，不支持抗锯齿。

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);

Paint paint = new Paint();

mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.pic);
mPath = new Path();

mPath.addCircle(mBitmap.getWidth() / 2, mBitmap.getHeight() / 2, mBitmap.getWidth() / 2, Path.Direction.CCW);
canvas.clipPath(mPath);
canvas.drawBitmap(mBitmap, 0, 0, paint);
}

2、使用PorterDuffXfermode

PorterDuffXfermode是Android主流的图片合成工具，支持模式多，稳定性强，效果好，质量高，支持抗锯齿备受广大开发者喜爱，可以说是很多应用开发的首选。缺点是难度学习有些高，另外比较占内存。

/**
* 绘制圆形图片
*
*/
@Override
protected void onDraw(Canvas canvas) {

Drawable drawable = getDrawable();
if (null != drawable) {
Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
Bitmap b = getCircleBitmap(bitmap);
final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
final Rect rectDest = new Rect(0,0,getWidth(),getHeight());
paint.reset();
canvas.drawBitmap(b, rectSrc, rectDest, paint);

} else {
super.onDraw(canvas);
}
}

/**
* 获取圆形图片方法
* @param bitmap
* @param pixels
* @return Bitmap
*/
private Bitmap getCircleBitmap(Bitmap bitmap) {
Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
bitmap.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(output);

final int color = 0xff424242;

final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
paint.setAntiAlias(true);
canvas.drawColor(Color.TRANSPARENT);
paint.setColor(color);
int x = bitmap.getWidth();

canvas.drawCircle(x / 2, x / 2, x / 2, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;

}
4、设置画笔Paint的Shader，然后用该画笔绘制圆形图片

该方法是Glide和picasso使用的方法，用法简单便捷，占内占有率处于中等水平。

@Override
protected void onDraw(Canvas canvas) {

Drawable drawable = getDrawable();
if (null != drawable) {
Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
Bitmap b = transform(bitmap);
final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
final Rect rectDest = new Rect(0,0,getWidth(),getHeight());
paint.reset();
canvas.drawBitmap(b, rectSrc, rectDest, paint);

} else {
super.onDraw(canvas);
}
}

public Bitmap transform(Bitmap source) {
int size = Math.min(source.getWidth(), source.getHeight());

int x = (source.getWidth() - size) / 2;
int y = (source.getHeight() - size) / 2;

Bitmap squaredBitmap = Bitmap.createBitmap(source, x, y, size, size);
if (squaredBitmap != source) {
source.recycle();
}

Bitmap bitmap = Bitmap.createBitmap(size, size, source.getConfig());

Canvas canvas = new Canvas(bitmap);
Paint paint = new Paint();
BitmapShader shader = new BitmapShader(squaredBitmap,
BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP);

float mScale = (mRadius * 2.0f) / Math.min(bitmap.getHeight(), bitmap.getWidth());

Matrix matrix = new Matrix();
matrix.setScale(mScale, mScale);
bitmapShader.setLocalMatrix(matrix);

paint.setShader(shader);
paint.setAntiAlias(true);

float r www.michenggw.com= size / 2f;
canvas.drawCircle(r, r, r, paint);

squaredBitmap.recycle();
return bitmap;
}
5、修改像素

该方法支持抗锯齿，用法简单，内存占有率同样处于中等水平。

public class CircleImageView extends AppCompatImageView {

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

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

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

@Override
public void onDraw(Canvas canvas) {

int width = getWidth();
int height = getHeight();

int minSize = Math.min(width,height)/2;
Drawable drawable www.dasheng178.com= getDrawable();
if(drawable!=null && minSize!=www.dfgjpt.com0) {

if(Math.min(drawable.getIntrinsicWidth(www.078881.cn/),drawable.getIntrinsicHeight())==0) {
super.onDraw(canvas);
return;
}

int intrinsicWidth = drawable.getIntrinsicWidth();
int intrinsicHeight = drawable.getIntrinsicHeight();

float R = Math.min(intrinsicWidth,intrinsicHeight)/2;

Bitmap bmp = Bitmap.createBitmap(intrinsicWidth, intrinsicHeight, Bitmap.Config.ARGB_8888);
Canvas targetCanvas = new Canvas(bmp);

drawable.draw(targetCanvas);

for (int y=0;y<intrinsicHeight;y++){
for (int x=0;www.18037.cnx<intrinsicWidth;x++){
if((Math.pow(www.17093.cn x-intrinsicWidth/2,2) + Math.pow(y-intrinsicHeight/2,2))<=Math.pow(R,2)){
continue;
}
bmp.setPixel(x,y, Color.TRANSPARENT);
}
}

Matrix imageMatrix = getImageMatrix();
if(imageMatrix!=null){
canvas.concat(imageMatrix);
}
final int saveCount = canvas.getSaveCount();
canvas.save();

if (getCropToPadding()) {
final int scrollX = getScrollX();
final int scrollY = getScrollY();
canvas.clipRect(scrollX + getPaddingLeft(), scrollY + getPaddingTop(),
scrollX + getRight() - getLeft() - getPaddingRight(),
scrollY + getBottom() - getTop() - getPaddingBottom());
}

canvas.translate(getPaddingLeft(www.60910.cn),getPaddingTop());

DrawFilter drawFilter = canvas.getDrawFilter();
canvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG|Paint.FILTER_BITMAP_FLAG));
canvas.drawBitmap(bmp,0,0,null);
canvas.setDrawFilter(drawFilter);

canvas.restoreToCount(saveCount);

bmp.recycle();

}else{
super.onDraw(canvas);