From image to BufferedImage to image-CodePudding

I'm trying to read a 256x256 image using ImageIO.read, transform it into a ByteArray, then into a BufferedImage, and back into an image file using ImageIO.write. It all seems to work as it should, but the final image is quite corrupted (although clearly still based on the original image. I can't find what's wrong in the process, I am suspicious of the scansize parameter, which I don't completely understand.

The idea is to manipulate pixels in between the reading and writing, but at the moment I can't even recreate the original image back into itself.

I attach the original image and the processed one below:

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

fun main(args: Array<String>) {
    val bImage = ImageIO.read(File("original.tiff"))
    val bos = ByteArrayOutputStream()
    ImageIO.write(bImage, "tiff", bos)
    val data = bos.toByteArray()
    val width = 256
    val height = 256
    val bytesPerPixel = 3
    val len = width * height * bytesPerPixel
    val image = BufferedImage(width, height, BufferedImage.TYPE_INT_RGB)
    val arr = IntArray(len)

    for (i in 0 until len) arr[i] = data.get(i).toInt()

    image.setRGB(0, 0, width, height, arr, 0, 256) // Seems like something is wrong here

    try {
        ImageIO.write(image, "jpg", File("converted-grayscale-002.jpg"))
    } catch (e: IOException) {
        System.err.println("IOException: $e")
    }
}

CodePudding user response：

This line is not returning the RGB image data:

val data = bos.toByteArray()

it is returning the compressed stream of the image in tiff format, surely it is not the correct image.

To get the pixels, use Image.getPixel(), alternatively you can get the buffer of the image directly, but to this you need to know what is the underlying buffer type - this is broad topic.

Take a look at this answer, it should give you idea how to do it: convert a RGB image to grayscale Image reducing the memory in java