Adaptive centering picture (Based on Java. Writing with Kotlin)

adaptiveCenter.kt

package com.voyageone.components.s7.template.analysis.viewer

import java.awt.image.BufferedImage
import java.io.ByteArrayInputStream
import java.io.ByteArrayOutputStream
import java.io.InputStream
import javax.imageio.ImageIO

fun adaptiveCenterAsStream(imageInputStream: InputStream, size: String): InputStream = adaptiveCenterAsImage(imageInputStream, size).let {
    val os = ByteArrayOutputStream()
    ImageIO.write(it, "png", os)
    return ByteArrayInputStream(os.toByteArray())
}

fun adaptiveCenterAsImage(imageInputStream: InputStream, size: String): BufferedImage = SizeHelper(size).let {
    return adaptiveCenterAsImage(imageInputStream, it)
}

fun adaptiveCenterAsImage(imageInputStream: InputStream, size: SizeHelper): BufferedImage = ImageIO.read(imageInputStream).let {
    return adaptiveCenter(it, size.width, size.height)
}

/**
 * 自适应居中图片到目标大小的画布上
 */
fun adaptiveCenter(image: BufferedImage, newWidth: Double, newHeight: Double): BufferedImage {
    val bufferedWidth = newWidth
    val bufferedHeight = newHeight
    val widthScale = bufferedWidth / image.width
    val heightScale = bufferedHeight / image.height
    val width: Double
    val height: Double
    val x: Double
    val y: Double

    when {
        widthScale >= 1 && heightScale >= 1 -> {
            // 图片和画布都是等比，并且图片小于画布
            // 则不需要处理，直接居中即可
            width = image.width.toDouble()
            height = image.height.toDouble()
            x = (bufferedWidth - width) / 2
            y = (bufferedHeight - height) / 2
        }
        widthScale > heightScale -> {
            // 图片比画布稍大
            // 并且高度的缩放幅度大于宽度的
            // 所以按高度比例进行缩放
            width = image.width * heightScale
            height = bufferedHeight
            x = (bufferedWidth - width) / 2
            y = 0.0
        }
        widthScale < heightScale -> {
            // 图片比画布稍大
            // 并且宽度的缩放幅度大于高度的
            // 所以按宽度比例进行缩放
            width = bufferedWidth
            height = image.height * widthScale
            x = 0.0
            y = (bufferedHeight - height) / 2
        }
        else -> {
            // 图片比画布大
            // 并且两边比例相同
            width = bufferedWidth
            height = bufferedHeight
            x = 0.0
            y = 0.0
        }
    }

    val bufferedImage = BufferedImage(bufferedWidth.toInt(), bufferedHeight.toInt(), BufferedImage.TYPE_INT_ARGB)
    val g2d = bufferedImage.graphics
    g2d.drawImage(image, x.toInt(), y.toInt(), width.toInt(), height.toInt(), null)
    g2d.dispose()
    return bufferedImage
}