CombineBitmaps.kt

/**
 * 拼接bitmap
 * @param bgColor 画布颜色，默认为null，透明色
 */
fun combineBitmaps(vararg bitmaps: Bitmap, bgColor: Int? = null, direction: CombineDirection = CombineDirection.Vertical, maxLength: Int? = null): Bitmap {
    var height = 0
    var width = 0
    // 计算组合后宽高
    loop@ for (bitmap in bitmaps) {
        when (direction) {
            CombineDirection.Horizontal -> {
                width += bitmap.width
                if (maxLength != null) continue@loop
                if (bitmap.height > height) {
                    height = bitmap.height
                }
            }
            CombineDirection.Vertical -> {
                height += bitmap.height
                if (maxLength != null) continue@loop
                if (bitmap.width > width) {
                    width = bitmap.width
                }
            }
        }
    }
    maxLength?.let {
        when (direction) {
            CombineDirection.Horizontal -> height = maxLength
            CombineDirection.Vertical -> width = maxLength
        }
    }
    val bigBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
    val bigCanvas = Canvas(bigBitmap)
    // draw background if necessary
    bgColor?.let { bigCanvas.drawColor(it) }
    var iOffset = 0f
    for (bitmap in bitmaps) {
        iOffset += when (direction) {
            CombineDirection.Horizontal -> {
                bigCanvas.drawBitmap(bitmap, iOffset, (height - bitmap.height) * 0.5f, Paint())
                bitmap.width
            }
            CombineDirection.Vertical -> {
                bigCanvas.drawBitmap(bitmap, (width - bitmap.width) * 0.5f, iOffset, Paint())
                bitmap.height
            }
        }
    }
    return bigBitmap
}

enum class CombineDirection {
    Vertical,
    Horizontal,
}