对jpeg映像进行删除，并将其在kotlin（至少80％）中恢复为原始图像 已经使用Kotlin创建了一个应用程序，该应用程序将要求用户从图库中选择图像。然后，用户具有两个按钮压缩图像和解压缩图像。 现在的问题是，当我们是

Question

import android.content.Intent
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.net.Uri
import android.os.Bundle
import android.provider.MediaStore
import android.widget.Button
import android.widget.ImageView
import android.widget.Toast
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity
import java.io.ByteArrayOutputStream
import java.io.IOException

class MainActivity : AppCompatActivity() {

    private lateinit var displayImage: ImageView  //image selected
    private lateinit var compressedImageView: ImageView   //image after compression or                 decompression
    private lateinit var selectImage: Button  // button for selecting image from gallery
    private lateinit var compressButton: Button   // button to start compression
    private lateinit var decompressButton: Button  //  Button to start decompression
    private var imageUri: Uri? = null
    private var compressedImageBytes: ByteArray? = null
    private var decompressedImageBytes: ByteArray? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        displayImage = findViewById(R.id.imageView)
        compressedImageView = findViewById(R.id.imageView2)
        selectImage = findViewById(R.id.upload)
        compressButton = findViewById(R.id.uploadWithCompress)
        decompressButton = findViewById(R.id.decompressImage)

        selectImage.setOnClickListener {
            val intent = Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI)
            pickImageLauncher.launch(intent)
        }

        compressButton.setOnClickListener {
            imageUri?.let { compressImage(it) }
        }

        decompressButton.setOnClickListener {
            compressedImageBytes?.let { decompressImage(it) }
        }
    }

    private val pickImageLauncher = registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
        if (result.resultCode == RESULT_OK) {
            result.data?.data?.let {
                imageUri = it
                displayImage.setImageURI(it)
            }
        }
    }

    private fun compressImage(uri: Uri) {
        try {
            val bmp = MediaStore.Images.Media.getBitmap(contentResolver, uri)
            val baos = ByteArrayOutputStream()
            bmp.compress(Bitmap.CompressFormat.JPEG, 25, baos)
            compressedImageBytes = baos.toByteArray()

            val compressedBitmap = BitmapFactory.decodeByteArray(compressedImageBytes, 0, compressedImageBytes!!.size)
            compressedImageView.setImageBitmap(compressedBitmap)

            val compressedSizeKB = compressedImageBytes!!.size / 1024
            Toast.makeText(this, "Compressed Image Size: $compressedSizeKB KB", Toast.LENGTH_SHORT).show()
        } catch (e: IOException) {
            e.printStackTrace()
        }
    }

    private fun decompressImage(compressedBytes: ByteArray) {
        val decompressedBitmap = BitmapFactory.decodeByteArray(compressedBytes, 0, compressedBytes.size)
        compressedImageView.setImageBitmap(decompressedBitmap)

        val decompressedSizeKB = compressedImageBytes!!.size / 1024
        Toast.makeText(this, "Image Decompressed to Original Quality and its size is: $decompressedSizeKB KB", Toast.LENGTH_SHORT).show()
    }
}

现在，现在几乎不可能将压缩图像的原始质量重新恢复到其原始形式，但是如果可以使用任何外部工具，请在此处共享。

图像压缩技术有两种类型的损失和无损。有损技术将永久删除图像的细节，并且无法逆转，这意味着解剖图像将与原始图像相同。而无损会压缩图像而不会影响图像的质量，从而使原始图像在减压后完全还原。

jpeg

Bitmap.CompressFormat.JPEG

始终是一种有损的压缩，这意味着一些细节被丢弃。如果您想压缩图像并以相同的形式检索而没有任何质量损失，请尝试使用PNG

Bitmap.CompressFormat.PNG

或WebP无损

Bitmap.CompressFormat.WEBP_LOSSLESS

Answer 1

参考： -

does bitmapfactory.decodefile（）文件解码时jpeg映像解压缩？