Android画布Canvas绘制drawBitmap基于源Rect和目的Rect，Kotlin

Android画布Canvas绘制drawBitmap基于源Rect和目的Rect，Kotlin

import android.graphics.Bitmap
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Rect
import android.graphics.drawable.BitmapDrawable
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.ImageView
import androidx.lifecycle.lifecycleScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch

class MainActivity : AppCompatActivity() {
    private var iv: ImageView? = null
    private var iv1: ImageView? = null
    private var iv2: ImageView? = null
    private var iv3: ImageView? = null
    private var iv4: ImageView? = null
    private var iv5: ImageView? = null
    private var iv6: ImageView? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        iv = findViewById(R.id.iv)
        iv1 = findViewById(R.id.iv1)
        iv2 = findViewById(R.id.iv2)
        iv3 = findViewById(R.id.iv3)
        iv4 = findViewById(R.id.iv4)
        iv5 = findViewById(R.id.iv5)
        iv6 = findViewById(R.id.iv6)

        lifecycleScope.launch(Dispatchers.Main) {
            delay(500)

            capture1()
            capture2()
            capture3()
            capture4()
            capture5()
            capture6()
        }
    }

    private fun capture1() {
        val srcBmp = (iv!!.drawable as BitmapDrawable).bitmap

        //创建一个和srcBmp宽高相同背景为Color.LTGRAY空Bitmap
        val bitmap = Bitmap.createBitmap(srcBmp!!.width, srcBmp!!.height, Bitmap.Config.ARGB_8888);
        val canvas = Canvas(bitmap)
        canvas.drawColor(Color.LTGRAY)

        val dstW = srcBmp!!.width / 4
        val dstH = srcBmp!!.height / 2
        val dstRect = Rect(0, 0, dstW, dstH) //bitmap坐标
        canvas.drawBitmap(
            srcBmp,
            null,
            dstRect,
            null
        )

        iv1!!.setImageBitmap(bitmap)
    }

    private fun capture2() {
        val srcBmp = (iv!!.drawable as BitmapDrawable).bitmap

        val bitmap = Bitmap.createBitmap(srcBmp!!.width, srcBmp!!.height, Bitmap.Config.ARGB_8888)
        val canvas = Canvas(bitmap)
        canvas.drawColor(Color.GREEN)

        //复制一个宽1/2和高1/2的原图。
        val dstW = srcBmp!!.width / 2
        val dstH = srcBmp!!.height / 2

        //框住原图中心点右下1/4部分。
        val srcRect = Rect(dstW, dstH, srcBmp!!.width, srcBmp!!.height)

        //bitmap左上角偏移20开始摆放。
        val dstRect = Rect(20, 20, dstW + 20, dstH + 20)
        canvas.drawBitmap(
            srcBmp,
            srcRect,
            dstRect,
            null
        )

        iv2!!.setImageBitmap(bitmap)
    }

    private fun capture3() {
        val srcBmp = (iv!!.drawable as BitmapDrawable).bitmap

        val bitmap = Bitmap.createBitmap(srcBmp!!.width, srcBmp!!.height, Bitmap.Config.ARGB_8888)
        val canvas = Canvas(bitmap)
        canvas.drawColor(Color.CYAN)

        val dstW = srcBmp!!.width / 2
        val dstH = srcBmp!!.height / 2

        val centerX = srcBmp!!.width / 2
        val centerY = srcBmp!!.height / 2

        //框住原图右上1/4部分，坐标仍以原图为准。
        val srcRect = Rect(centerX, 0, centerX + srcBmp!!.width / 2, centerY)

        //摆放到bitmap的中心位置。
        val dstRect = Rect(centerX - dstW / 2, centerY - dstH / 2, centerX + dstW / 2, centerY + dstH / 2)

        canvas.drawBitmap(
            srcBmp,
            srcRect,
            dstRect,
            null
        )

        iv3!!.setImageBitmap(bitmap)
    }

    private fun capture4() {
        val srcBmp = (iv!!.drawable as BitmapDrawable).bitmap

        val w = srcBmp!!.width / 2
        val h = srcBmp!!.height / 2

        val bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888)
        val canvas = Canvas(bitmap)
        canvas.drawColor(Color.YELLOW)

        val centerX = srcBmp!!.width / 2
        val centerY = srcBmp!!.height / 2

        //框住原图中心1/2部分，坐标仍以原图为准。
        val srcRect = Rect(centerX - w / 2, centerY - h / 2, centerX + w / 2, centerY + h / 2)

        //直接摆放到bitmap。
        val dstRect = Rect(0, 0, w, h)

        canvas.drawBitmap(
            srcBmp,
            srcRect,
            dstRect,
            null
        )

        iv4!!.setImageBitmap(bitmap)
    }

    //截取原图右下1/3的部分
    private fun capture5() {
        val srcBmp = (iv!!.drawable as BitmapDrawable).bitmap

        val w = srcBmp!!.width / 3
        val h = srcBmp!!.height / 3

        val bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888)
        val canvas = Canvas(bitmap)
        canvas.drawColor(Color.RED)

        val left = (srcBmp!!.width / 3) * 2
        val top = (srcBmp!!.height / 3) * 2

        //框住原图右下1/3部分，坐标仍以原图为准
        val srcRect = Rect(left, top, left + w, top + h)

        //直接摆放到bitmap。
        val dstRect = Rect(0, 0, w, h)

        canvas.drawBitmap(
            srcBmp,
            srcRect,
            dstRect,
            null
        )

        iv5!!.setImageBitmap(bitmap)
    }

    //截取原图左侧中间1/3部分
    private fun capture6() {
        val srcBmp = (iv!!.drawable as BitmapDrawable).bitmap

        val w = srcBmp!!.width / 3
        val h = srcBmp!!.height / 3

        val bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888)
        val canvas = Canvas(bitmap)
        canvas.drawColor(Color.BLUE)

        val top = srcBmp!!.height / 3

        //框住原图部分。
        val srcRect = Rect(0, top, 0 + w, top + h)

        //直接摆放到bitmap。
        val dstRect = Rect(0, 0, w, h)

        canvas.drawBitmap(
            srcBmp,
            srcRect,
            dstRect,
            null
        )

        iv6!!.setImageBitmap(bitmap)
    }
}

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