在Android中,ImageView默认是一个矩形。如何使它成为一个圆角矩形(剪辑我的位图的所有4个角为圆角矩形)在ImageView?


请注意,从2021年起,只需使用ShapeableImageView


当前回答

对于上面提到的乔治·沃尔特斯二世,我只是把他的答案扩展了一下,以支持不同的圆角。这可以进一步优化(一些目标矩形重叠),但不是很多。

我知道这个线程有点老了,但它是谷歌上关于如何在Android上圆角ImageViews的查询的顶级结果之一。

/**
 * Use this method to scale a bitmap and give it specific rounded corners.
 * @param context Context object used to ascertain display density.
 * @param bitmap The original bitmap that will be scaled and have rounded corners applied to it.
 * @param upperLeft Corner radius for upper left.
 * @param upperRight Corner radius for upper right.
 * @param lowerRight Corner radius for lower right.
 * @param lowerLeft Corner radius for lower left.
 * @param endWidth Width to which to scale original bitmap.
 * @param endHeight Height to which to scale original bitmap.
 * @return Scaled bitmap with rounded corners.
 */
public static Bitmap getRoundedCornerBitmap(Context context, Bitmap bitmap, float upperLeft,
        float upperRight, float lowerRight, float lowerLeft, int endWidth,
        int endHeight) {
    float densityMultiplier = context.getResources().getDisplayMetrics().density;

    // scale incoming bitmap to appropriate px size given arguments and display dpi
    bitmap = Bitmap.createScaledBitmap(bitmap, 
            Math.round(endWidth * densityMultiplier),
            Math.round(endHeight * densityMultiplier), true);

    // create empty bitmap for drawing
    Bitmap output = Bitmap.createBitmap(
            Math.round(endWidth * densityMultiplier),
            Math.round(endHeight * densityMultiplier), Config.ARGB_8888);

    // get canvas for empty bitmap
    Canvas canvas = new Canvas(output);
    int width = canvas.getWidth();
    int height = canvas.getHeight();

    // scale the rounded corners appropriately given dpi
    upperLeft *= densityMultiplier;
    upperRight *= densityMultiplier;
    lowerRight *= densityMultiplier;
    lowerLeft *= densityMultiplier;

    Paint paint = new Paint();
    paint.setAntiAlias(true);
    paint.setColor(Color.WHITE);

    // fill the canvas with transparency
    canvas.drawARGB(0, 0, 0, 0);

    // draw the rounded corners around the image rect. clockwise, starting in upper left.
    canvas.drawCircle(upperLeft, upperLeft, upperLeft, paint);
    canvas.drawCircle(width - upperRight, upperRight, upperRight, paint);
    canvas.drawCircle(width - lowerRight, height - lowerRight, lowerRight, paint);
    canvas.drawCircle(lowerLeft, height - lowerLeft, lowerLeft, paint);

    // fill in all the gaps between circles. clockwise, starting at top.
    RectF rectT = new RectF(upperLeft, 0, width - upperRight, height / 2);
    RectF rectR = new RectF(width / 2, upperRight, width, height - lowerRight);
    RectF rectB = new RectF(lowerLeft, height / 2, width - lowerRight, height);
    RectF rectL = new RectF(0, upperLeft, width / 2, height - lowerLeft);

    canvas.drawRect(rectT, paint);
    canvas.drawRect(rectR, paint);
    canvas.drawRect(rectB, paint);
    canvas.drawRect(rectL, paint);

    // set up the rect for the image
    Rect imageRect = new Rect(0, 0, width, height);

    // set up paint object such that it only paints on Color.WHITE
    paint.setXfermode(new AvoidXfermode(Color.WHITE, 255, AvoidXfermode.Mode.TARGET));

    // draw resized bitmap onto imageRect in canvas, using paint as configured above
    canvas.drawBitmap(bitmap, imageRect, imageRect, paint);

    return output;
}

其他回答

相当多的答案!

我遵循了一些人也建议的这个例子:http://www.techrepublic.com/article/pro-tip-round-corners-on-an-android-imageview-with-this-hack/

然而,我需要的是一个透明图像后面的彩色圆圈。对于任何有兴趣做同样事情的人…

1)设置FrameLayout的宽度和高度-在我的情况下,图像的大小(50dp)。 2)将带有src = "@drawable/…"的ImageView放在带有图像的ImageView之上。给它一个id,在我的例子中,我叫它iconShape 3) Drawable mask.xml应该是纯色的#ffffffff 4)如果你想在你的代码中动态地改变圆圈的颜色,可以这样做

ImageView iv2 = (ImageView) v.findViewById(R.id.iconShape);
Drawable shape = getResources().getDrawable(R.drawable.mask);
shape.setColorFilter(Color.BLUE, Mode.MULTIPLY);
iv2.setImageDrawable(shape);

如果你不希望边框影响图像,使用这个类。不幸的是,我没有找到任何方法来绘制画布上的透明区域来到onDraw()。这里创建了一个新的位图它是画在一个真实的画布上的。

如果您想要创建一个消失的边界,该视图非常有用。如果你将borderWidth设置为0,边框将会消失,图像仍然保持圆角,就像边界一样。也就是说,它看起来就像边界完全由图像边缘绘制。

import android.annotation.SuppressLint
import android.content.Context
import android.graphics.Bitmap
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.graphics.PorterDuff
import android.graphics.PorterDuffXfermode
import android.graphics.RectF
import android.util.AttributeSet
import androidx.appcompat.widget.AppCompatImageView


class RoundedImageViewWithBorder @JvmOverloads constructor(
        context: Context,
        attrs: AttributeSet? = null,
        defStyleAttr: Int = 0) : AppCompatImageView(context, attrs, defStyleAttr) {

    var borderColor: Int = 0
        set(value) {
            invalidate()
            field = value
        }
    var borderWidth: Int = 0
        set(value) {
            invalidate()
            field = value
        }
    var cornerRadius: Float = 0f
        set(value) {
            invalidate()
            field = value
        }

    private var bitmapForDraw: Bitmap? = null
    private var canvasForDraw: Canvas? = null
    private val transparentPaint = Paint().apply {
        isAntiAlias = true
        color = Color.TRANSPARENT
        style = Paint.Style.STROKE
        xfermode = PorterDuffXfermode(PorterDuff.Mode.SRC)
    }

    private val borderPaint = Paint().apply {
        isAntiAlias = true
        style = Paint.Style.STROKE
    }

    private val transparentAreaRect = RectF()
    private val borderRect = RectF()

    init {
        val typedArray = context.obtainStyledAttributes(attrs, R.styleable.RoundedImageViewWithBorder)

        try {
            borderWidth = typedArray.getDimensionPixelSize(R.styleable.RoundedImageViewWithBorder_border_width, 0)
            borderColor = typedArray.getColor(R.styleable.RoundedImageViewWithBorder_border_color, 0)
            cornerRadius = typedArray.getDimensionPixelSize(R.styleable.RoundedImageViewWithBorder_corner_radius, 0).toFloat()

        } finally {
            typedArray.recycle()
        }
    }

    @SuppressLint("CanvasSize", "DrawAllocation")
    override fun onDraw(canvas: Canvas) {
        if (canvas.height <=0 || canvas.width <=0) {
            return
        }

        if (canvasForDraw?.height != canvas.height || canvasForDraw?.width != canvas.width) {
            val newBitmap = Bitmap.createBitmap(canvas.width, canvas.height, Bitmap.Config.ARGB_8888)
            bitmapForDraw = newBitmap
            canvasForDraw = Canvas(newBitmap)
        }
        
        bitmapForDraw?.eraseColor(Color.TRANSPARENT)

        // Draw existing content
        super.onDraw(canvasForDraw)

        if (borderWidth > 0) {
            canvasForDraw?.let { drawWithBorder(it) }
        } else {
            canvasForDraw?.let { drawWithoutBorder(it) }
        }

        // Draw everything on real canvas
        bitmapForDraw?.let { canvas.drawBitmap(it, 0f, 0f, null) }
    }

    private fun drawWithBorder(canvas: Canvas) {
        // Draw transparent area
        transparentPaint.strokeWidth = borderWidth.toFloat() * 4
        transparentAreaRect.apply {
            left = -borderWidth.toFloat() * 1.5f
            top = -borderWidth.toFloat() * 1.5f
            right = canvas.width.toFloat() + borderWidth.toFloat() * 1.5f
            bottom = canvas.height.toFloat() + borderWidth.toFloat() * 1.5f
        }
        canvasForDraw?.drawRoundRect(transparentAreaRect, borderWidth.toFloat() * 2 + cornerRadius, borderWidth.toFloat() * 2 + cornerRadius, transparentPaint)

        // Draw border
        borderPaint.color = borderColor
        borderPaint.strokeWidth = borderWidth.toFloat()
        borderRect.apply {
            left = borderWidth.toFloat() / 2
            top = borderWidth.toFloat() / 2
            right = canvas.width.toFloat() - borderWidth.toFloat() / 2
            bottom = canvas.height.toFloat() - borderWidth.toFloat() / 2
        }
        canvas.drawRoundRect(borderRect, cornerRadius - borderWidth.toFloat() / 2, cornerRadius - borderWidth.toFloat() / 2, borderPaint)
    }

    private fun drawWithoutBorder(canvas: Canvas) {
        // Draw transparent area
        transparentPaint.strokeWidth = cornerRadius * 4
        transparentAreaRect.apply {
            left = -cornerRadius * 2
            top = -cornerRadius * 2
            right = canvas.width.toFloat() + cornerRadius * 2
            bottom = canvas.height.toFloat() + cornerRadius * 2
        }
        canvasForDraw?.drawRoundRect(transparentAreaRect, cornerRadius * 3, cornerRadius * 3, transparentPaint)
    }

}

值:

<declare-styleable name="RoundedImageViewWithBorder">
    <attr name="corner_radius" format="dimension|string" />
    <attr name="border_width" format="dimension|reference" />
    <attr name="border_color" format="color|reference" />
</declare-styleable>

对于上面提到的乔治·沃尔特斯二世,我只是把他的答案扩展了一下,以支持不同的圆角。这可以进一步优化(一些目标矩形重叠),但不是很多。

我知道这个线程有点老了,但它是谷歌上关于如何在Android上圆角ImageViews的查询的顶级结果之一。

/**
 * Use this method to scale a bitmap and give it specific rounded corners.
 * @param context Context object used to ascertain display density.
 * @param bitmap The original bitmap that will be scaled and have rounded corners applied to it.
 * @param upperLeft Corner radius for upper left.
 * @param upperRight Corner radius for upper right.
 * @param lowerRight Corner radius for lower right.
 * @param lowerLeft Corner radius for lower left.
 * @param endWidth Width to which to scale original bitmap.
 * @param endHeight Height to which to scale original bitmap.
 * @return Scaled bitmap with rounded corners.
 */
public static Bitmap getRoundedCornerBitmap(Context context, Bitmap bitmap, float upperLeft,
        float upperRight, float lowerRight, float lowerLeft, int endWidth,
        int endHeight) {
    float densityMultiplier = context.getResources().getDisplayMetrics().density;

    // scale incoming bitmap to appropriate px size given arguments and display dpi
    bitmap = Bitmap.createScaledBitmap(bitmap, 
            Math.round(endWidth * densityMultiplier),
            Math.round(endHeight * densityMultiplier), true);

    // create empty bitmap for drawing
    Bitmap output = Bitmap.createBitmap(
            Math.round(endWidth * densityMultiplier),
            Math.round(endHeight * densityMultiplier), Config.ARGB_8888);

    // get canvas for empty bitmap
    Canvas canvas = new Canvas(output);
    int width = canvas.getWidth();
    int height = canvas.getHeight();

    // scale the rounded corners appropriately given dpi
    upperLeft *= densityMultiplier;
    upperRight *= densityMultiplier;
    lowerRight *= densityMultiplier;
    lowerLeft *= densityMultiplier;

    Paint paint = new Paint();
    paint.setAntiAlias(true);
    paint.setColor(Color.WHITE);

    // fill the canvas with transparency
    canvas.drawARGB(0, 0, 0, 0);

    // draw the rounded corners around the image rect. clockwise, starting in upper left.
    canvas.drawCircle(upperLeft, upperLeft, upperLeft, paint);
    canvas.drawCircle(width - upperRight, upperRight, upperRight, paint);
    canvas.drawCircle(width - lowerRight, height - lowerRight, lowerRight, paint);
    canvas.drawCircle(lowerLeft, height - lowerLeft, lowerLeft, paint);

    // fill in all the gaps between circles. clockwise, starting at top.
    RectF rectT = new RectF(upperLeft, 0, width - upperRight, height / 2);
    RectF rectR = new RectF(width / 2, upperRight, width, height - lowerRight);
    RectF rectB = new RectF(lowerLeft, height / 2, width - lowerRight, height);
    RectF rectL = new RectF(0, upperLeft, width / 2, height - lowerLeft);

    canvas.drawRect(rectT, paint);
    canvas.drawRect(rectR, paint);
    canvas.drawRect(rectB, paint);
    canvas.drawRect(rectL, paint);

    // set up the rect for the image
    Rect imageRect = new Rect(0, 0, width, height);

    // set up paint object such that it only paints on Color.WHITE
    paint.setXfermode(new AvoidXfermode(Color.WHITE, 255, AvoidXfermode.Mode.TARGET));

    // draw resized bitmap onto imageRect in canvas, using paint as configured above
    canvas.drawBitmap(bitmap, imageRect, imageRect, paint);

    return output;
}

为了Glide 4.x.x

使用下面的简单代码

Glide
  .with(context)
  .load(uri)
  .apply(
      RequestOptions()
        .circleCrop())
  .into(imageView)

对于那些使用Glide和Kotlin的,你可以通过扩展RequestBuilder来实现

fun <T> GlideRequest<T>.roundCorners(cornerRadius: Int) =
    apply(RequestOptions().transform(RoundedCorners(cornerRadius)))

并使用as;

 GlideApp.with(context)
            .load(url)
            .roundCorners(context.resources.getDimension(R.dimen.radius_in_dp).toInt())
            .into(imgView)