[Java, Scala] Image resizing with ImageIO

Whole code

import java.io.File
import java.awt.image.BufferedImage
import javax.imageio.ImageIO

object ImageUtil {
  def resize(file: File): Unit = {
    val original = ImageIO.read(file)

    //Vertical and horizontal size of the original file(pixel)Get
    val originalWidth = original.getWidth.toDouble
    val originalHeight = original.getHeight.toDouble

    //Get the aspect ratio with the long side as 1
    val (widthScale, heightScale) =
      if(originalWidth > originalHeight) (1d, originalHeight / originalWidth)
      else (originalWidth / originalHeight, 1d)

    //Set the long side to 200px, maintain the aspect ratio, and determine the image size after resizing.
    val width = (200d * widthScale).toInt
    val height = (200d * heightScale).toInt

    val image = new BufferedImage(width, height, original.getType)

    val scaled = original.getScaledInstance(width, height, java.awt.Image.SCALE_AREA_AVERAGING)

    image.getGraphics.drawImage(scaled, 0, 0, width, height, null)

    ImageIO.write(image, "jpeg", new File("/tmp/resized.jpeg "))
  }
}

Rough commentary

I think that there is no problem in calculating the image size, so only the image generation part.

val image = new BufferedImage(width, height, original.getType)

The image size is determined here. An image of making a clean canvas. In the example, the image is adjusted to the size of the resized image, so the image has no margins. If you want to make a square with a margin, it looks like this.

//Make a square with the length of the long side as one side
val scale = Math.max(width, height)
val image = new BufferedImage(scale, scale, original.getType)

Next, the image data obtained by resizing the original image is acquired.

val scaled = original.getScaledInstance(width, height, java.awt.Image.SCALE_AREA_AVERAGING)

Then paste the resized image on the canvas you made first.

image.getGraphics.drawImage(scaled, 0, 0, width, height, null)

0 and 0 are the x and y coordinates of the canvas, respectively. An image to paste the image after resizing based on the specified coordinates. If there is a margin, you can adjust the coordinates to move the image to the left, right, top, bottom, or center.

Finally, output the file and finish.

ImageIO.write(image, "jpeg", new File("/tmp/resized.jpeg "))

Bonus: Change the color of the margins

If there is a margin, the color of the margin is black by default. If you want to change the color, you can paint the whole thing with your favorite color before drawImage.

//Make the margin white
image.getGraphics.setColor(Color.WHITE)

//Coordinate(0, 0)From, fill the entire height and width of the image with the specified color
image.getGraphics.fillRect(0, 0, image.getWidth, image.getHeight)