XML文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center">
    <ImageView
        android:id="@+id/iv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

Activity代码

const val TAG = "Yang"
class MainActivity : AppCompatActivity() {
    var screenWidth = 0
    var screenHeight = 0
    var mImageView: ImageView ?= null
    var tempBitmap: Bitmap? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        mImageView = findViewById(R.id.iv)
        // 屏幕宽高的一半作为临时RectF, 用于压缩Bitmap
        screenWidth = resources.displayMetrics.widthPixels
        screenHeight = resources.displayMetrics.heightPixels
        val tempRect = RectF(0f, 0f, screenWidth.toFloat() / 2, screenHeight.toFloat() / 2)

        CoroutineScope(Dispatchers.IO).launch {
            tempBitmap = getBitmap(resources, tempRect, R.drawable.fake)
            withContext(Dispatchers.Main) {
                mImageView?.post {
                    tempBitmap?.let {
                        mImageView?.setImageBitmap(splitAndDrawBitmapWithMatrix(it, 10, 10))
                    }
                }
            }
        }
    }
}

fun getBitmap(resources : Resources, destRect : RectF, imageId: Int): Bitmap? {
    var imageWidth = -1
    var imageHeight = -1
    val preOption = BitmapFactory.Options().apply {
        // 只获取图片的宽高
        inJustDecodeBounds = true
        BitmapFactory.decodeResource(resources, imageId, this)
    }
    imageWidth = preOption.outWidth
    imageHeight = preOption.outHeight
    // 计算缩放比例
    val scaleMatrix = Matrix()
    // 确定未缩放Bitmap的RectF
    var srcRect = RectF(0f, 0f, imageWidth.toFloat(), imageHeight.toFloat())
    // 通过目标RectF, 确定缩放数值，存储在scaleMatrix中
    scaleMatrix.setRectToRect(srcRect, destRect, Matrix.ScaleToFit.CENTER)
    // 缩放数值再映射到原始Bitmap上，得到缩放后的RectF
    scaleMatrix.mapRect(srcRect)

    val finalOption = BitmapFactory.Options().apply {
        if (imageHeight > 0 && imageWidth > 0) {
            inPreferredConfig = Bitmap.Config.ARGB_8888
            inSampleSize = calculateInSampleSize(
                imageWidth,
                imageHeight,
                srcRect.width().toInt(),
                srcRect.height().toInt()
            )
        }
    }
    return BitmapFactory.decodeResource(resources, imageId, finalOption)
}

fun calculateInSampleSize(fromWidth: Int, fromHeight: Int, toWidth: Int, toHeight: Int): Int {
    var bitmapWidth = fromWidth
    var bitmapHeight = fromHeight
    if (fromWidth > toWidth|| fromHeight > toHeight) {
        var inSampleSize = 1
        // 计算最大的inSampleSize值，该值是2的幂，并保持原始宽高大于目标宽高
        while (bitmapWidth >= toWidth && bitmapHeight >= toHeight) {
            bitmapWidth /= 2
            bitmapHeight /= 2
            inSampleSize *= 2
        }
        return inSampleSize
    }
    return 1
}

Canvas平移方式绘制

• 保证每次从左上角原点开始绘制，每次绘制需要调用canvas.save()和canvas.restore()

fun splitAndDrawBitmapWithCanvas(input: Bitmap, rows: Int, cols: Int): Bitmap {
    // 计算每个小格子的大小
    val width = input.width / cols
    val height = input.height / rows
    // 创建一个新的Bitmap，大小等于原始Bitmap
    val output = Bitmap.createBitmap(input.width, input.height, input.config)
    // 创建一个Canvas，关联到output Bitmap上
    val canvas = Canvas(output)
    // 创建一个画笔，设置抗锯齿和滤波
    val paint = Paint().apply {
        isAntiAlias = true
        isFilterBitmap = true
    }

    // 遍历每一行和每一列
    for (i in 0 until rows) {
        for (j in 0 until cols) {
            // 每隔一个格子进行绘制
            if ((i + j) % 2 == 0) {
                // 计算当前小格子的位置
                val x = j * width
                val y = i * height

                // 计算当前小格子的绘制区域
                val srcRect = Rect(x, y, x + width, y + height)
                val destRect = Rect(0, 0, width, height)
                canvas.save()
                // 使用Matrix来移动Canvas
                canvas.translate(x.toFloat(), y.toFloat())
                // 在Canvas上绘制当前的小格子
                canvas.drawBitmap(input, srcRect, destRect, paint)
                canvas.restore()
            }
        }
    }
    // 返回包含所有小格子的Bitmap
    return output
}

Rect方式绘制

 public void drawBitmap(@NonNull Bitmap bitmap, 
					 @Nullable Rect src, 
					 @NonNull Rect dst,
					 @Nullable Paint paint) {}

• src是原图中截取的矩形区域，如果设置为null，则默认截取整个原图
• dst是将 src截取的图像绘制到Canvas的哪个区域内

fun splitAndDrawBitmapWithRect(input: Bitmap, rows: Int, cols: Int): Bitmap {
    // 计算每个小格子的大小
    val width = input.width / cols
    val height = input.height / rows
    // 创建一个新的Bitmap，大小等于原始Bitmap
    val output = Bitmap.createBitmap(input.width, input.height, input.config)
    // 创建一个Canvas，关联到output Bitmap上
    val canvas = Canvas(output)
    // 创建一个画笔，设置抗锯齿和滤波
    val paint = Paint().apply {
        isAntiAlias = true
        isFilterBitmap = true
    }
    // 遍历每一行和每一列
    for (i in 0 until rows) {
        for (j in 0 until cols) {
            // 每隔一个格子进行绘制
            if ((i + j) % 2 == 0) {
                // 计算当前小格子的位置
                val x = j * width
                val y = i * height
                // 计算当前小格子的绘制区域
                val srcRect = Rect(x, y, x + width, y + height)
                val destRect = Rect(x, y, x + width, y + height)
                // 在Canvas上绘制当前的小格子
                canvas.drawBitmap(input, srcRect, destRect, paint)
            }
        }
    }
    // 返回包含所有小格子的Bitmap
    return output
}

效果图