这是圆形和矩形形状的解决方案。此外，它不仅适用于 Picasso 的使用，而且适用于一般的 android Canvas-tasks。
我已经创建了非常庞大和详细的它们，只是为了让您了解流程，随意缩短。
但我想澄清许多人面临的一个主要问题。
在 android 中没有可能创建内部或外部边框 - 仅居中：
这就是为什么你会收到这样的边框元素被截断的原因：
所以只有一种方法可以重新计算边框的位置：在
-
circle 你必须将圆的半径减小一半的边界宽度
-
矩形 你必须 1) 将边框线“向内”移动一半的边框宽度; 2) 将拐角半径减小一半边框宽度
这些操作将为您提供预期的结果：
如果您只需要边框代码 - 只选择通讯员 drawBorder() 方法。
这是一个带有两个图像的空片段的示例：
ViewsCroppingAndBorderingTestFragment.kt
class ViewsCroppingAndBorderingTestFragment : Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_test_views_cropping_and_bordering, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val urlCircle = "https://images-na.ssl-images-amazon.com/images/I/71zLQIfmTlL._AC_SX466_.jpg"
val urlRectRounded = "https://www.gardendesign.com/pictures/images/675x529Max/site_3/helianthus-yellow-flower-pixabay_11863.jpg"
val ivCircle = view.findViewById<ImageView>(R.id.ivCircle)
val ivRectRounded = view.findViewById<ImageView>(R.id.ivRectRounded)
val trCircle = CircleTransformation()
val trRectRounded = RectRoundedTransformation()
Picasso.get().load(urlCircle).transform(trCircle).into(ivCircle)
Picasso.get().load(urlRectRounded).transform(trRectRounded).into(ivRectRounded)
}
class CircleTransformation() : Transformation {
override fun transform(source: Bitmap): Bitmap {
val size = Math.min(source.width, source.height)
val x = (source.width - size) / 2
val y = (source.height - size) / 2
val w = size
val h = size
val squaredBitmap = Bitmap.createBitmap(source, x, y, w, h)
if (squaredBitmap != source) {
source.recycle()
}
val bitmap = Bitmap.createBitmap(w, h, source.config)
val canvas = Canvas(bitmap)
// >> Draw original rectangle image
// val paint = Paint(Paint.ANTI_ALIAS_FLAG)
// canvas.drawBitmap(squaredBitmap, 0F, 0F, paint)
val rImage = w / 2f
cropWithCircle(squaredBitmap, canvas, rImage)
squaredBitmap.recycle()
drawBorder(canvas, rImage)
return bitmap
}
private fun cropWithCircle(bitmapSource: Bitmap, canvas: Canvas, rImage: Float) {
val shader = BitmapShader(bitmapSource, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP)
val paint = Paint(Paint.ANTI_ALIAS_FLAG)
paint.shader = shader
paint.isAntiAlias = true
val xCenter = rImage
val yCenter = rImage
canvas.drawCircle(xCenter, yCenter, rImage, paint)
}
private fun drawBorder(canvas: Canvas, rImage: Float) {
val borderWidth = 30F
val paintBorder = Paint()
paintBorder.strokeWidth = borderWidth
paintBorder.style = Paint.Style.STROKE
paintBorder.color = Color.GREEN
paintBorder.isAntiAlias = true
val cCenter = rImage
val yCenter = rImage
// ANDROID'S BORDER IS ALWAYS CENTERED.
// So have to reduce radius by half of border's width
val rBorder = rImage - borderWidth / 2
canvas.drawCircle(cCenter, yCenter, rBorder, paintBorder)
}
override fun key(): String {
return "circle"
}
}
class RectRoundedTransformation() : Transformation {
override fun transform(source: Bitmap): Bitmap {
val x = 0
val y = 0
val w = source.width
val h = source.height
val squaredBitmap = Bitmap.createBitmap(source, x, y, w, h)
if (squaredBitmap != source) {
source.recycle()
}
val bitmap = Bitmap.createBitmap(w, h, source.config)
val canvas = Canvas(bitmap)
// >> Draw original rectangle image
// val paint = Paint(Paint.ANTI_ALIAS_FLAG)
// canvas.drawBitmap(squaredBitmap, 0F, 0F, paint)
val rCorner = 80F
cropCorners(squaredBitmap, canvas, rCorner)
squaredBitmap.recycle()
drawBorder(canvas, rCorner)
return bitmap
}
private fun cropCorners(bitmapSource: Bitmap, canvas: Canvas, rCorner: Float) {
val width = canvas.width
val height = canvas.height
val maskBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ALPHA_8)
val maskCanvas = Canvas(maskBitmap)
val maskPaint = Paint(Paint.ANTI_ALIAS_FLAG)
val maskRect = RectF(0F, 0F, width.toFloat(), height.toFloat())
// 1. draw base rect
maskCanvas.drawRect(maskRect, maskPaint)
// 2. cut off inner rounded rect, leave corners
maskPaint.xfermode = PorterDuffXfermode(PorterDuff.Mode.CLEAR)
maskCanvas.drawRoundRect(maskRect, rCorner, rCorner, maskPaint)
// 3. draw original rectangle image
val paintSource = Paint(Paint.ANTI_ALIAS_FLAG)
canvas.drawBitmap(bitmapSource, 0f, 0f, paintSource)
// 4.cut off corners
val paintCropped = Paint(Paint.ANTI_ALIAS_FLAG or Paint.FILTER_BITMAP_FLAG)
paintCropped!!.xfermode = PorterDuffXfermode(PorterDuff.Mode.CLEAR)
canvas.drawBitmap(maskBitmap!!, 0f, 0f, paintCropped)
}
private fun drawBorder(canvas: Canvas, rCorner: Float) {
val borderWidth = 30F
val paintBorder = Paint()
paintBorder.strokeWidth = borderWidth
paintBorder.style = Paint.Style.STROKE
paintBorder.color = Color.RED
paintBorder.isAntiAlias = true
// // ANDROID'S BORDER IS ALWAYS CENTERED.
// // So have to shift every side by half of border's width
val rectLeft = 0 + borderWidth / 2
val rectTop = 0 + borderWidth / 2
val rectRight = canvas.width.toFloat() - borderWidth / 2
val rectBottom = canvas.height.toFloat() - borderWidth / 2
val rectF = RectF(rectLeft, rectTop, rectRight, rectBottom)
// // So have to corner reduce radius by half of border's width
val rectRCorner = rCorner - borderWidth / 2
canvas.drawRoundRect(rectF, rectRCorner, rectRCorner, paintBorder)
}
override fun key(): String {
return "rectRounded"
}
}
}
fragment_test_views_cropping_and_bordering.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/temp"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="200dp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:background="@android:color/darker_gray">
<ImageView
android:id="@+id/ivCircle"
android:layout_width="150dp"
android:layout_height="150dp"
android:layout_margin="10dp"/>
<ImageView
android:id="@+id/ivRectRounded"
android:layout_width="200dp"
android:layout_height="160dp"
android:layout_margin="10dp"/>
</LinearLayout>