Android画布Canvas矩阵Matrix放大裁剪Rect区域的Bitmap，Kotlin

Android画布Canvas矩阵Matrix放大裁剪Rect区域的Bitmap，Kotlin

    private fun mydraw() {
        val originBmp = BitmapFactory.decodeResource(resources, R.mipmap.pic).copy(Bitmap.Config.ARGB_8888, true)

        val newBmp = Bitmap.createBitmap(originBmp.width, originBmp.height, Bitmap.Config.ARGB_8888)
        val canvas = Canvas(newBmp)

        //把原图绘制在画布Canvas
        //canvas.drawBitmap(originBmp, 0f, 0f, null)
        canvas.drawColor(Color.LTGRAY)

        val paint = Paint(Paint.ANTI_ALIAS_FLAG)
        paint.color = Color.BLUE
        paint.style = Paint.Style.STROKE
        paint.strokeWidth = 30f

        val centerX = originBmp.width / 2
        val centerY = originBmp.height / 2
        val w = 300
        val h = 200
        val rect = Rect((centerX - w / 2), (centerY - h / 2), (centerX + w / 2), (centerY + h / 2))
        val rectF = RectF(rect.left.toFloat(), rect.top.toFloat(), rect.right.toFloat(), rect.bottom.toFloat())

        canvas.clipRect(rect) //选（裁剪）出一块区域。
        canvas.drawRect(rect, paint) //在这块区域边框绘制线。

        canvas.drawBitmap(originBmp, null, rect, null)
        iv1?.setImageURI(Uri.fromFile(saveBitmapToFile(newBmp)))

        canvas.drawBitmap(originBmp, rect, rectF, null)
        iv2?.setImageURI(Uri.fromFile(saveBitmapToFile(newBmp)))

        val factor = 1.8f //放大系数
        val matrix = Matrix()
        matrix.setScale(factor, factor)

        canvas.drawBitmap(originBmp, matrix, null)
        iv3?.setImageURI(Uri.fromFile(saveBitmapToFile(newBmp)))

        canvas.translate(centerX - factor * originBmp.width / 2, centerY - factor * originBmp.height / 2)
        canvas.drawBitmap(originBmp, matrix, null)
        iv4?.setImageURI(Uri.fromFile(saveBitmapToFile(newBmp)))
    }

    private fun saveBitmapToFile(bm: Bitmap): File? {
        var saveFile: File? = null
        val savePath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).toString()
        if (!Files.exists(Paths.get(savePath))) {
            Log.d("保存文件", "${savePath}不存在!")
        } else {
            saveFile = File(savePath, System.currentTimeMillis().toString() + ".jpeg")
            try {
                val saveImgOut = FileOutputStream(saveFile)
                //压缩
                bm.compress(Bitmap.CompressFormat.JPEG, 90, saveImgOut)
                saveImgOut.flush()
                saveImgOut.close()
                Log.d("保存文件", "Bitmap保存至 ${saveFile.absoluteFile.toPath()}")
            } catch (e: Exception) {
                e.printStackTrace()
            }
        }

        return saveFile
    }

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