無法縮小灰度圖像

Question

我有一個256 * 256維度的灰度圖像。我試圖將其縮小到128 * 128。 我正在取兩個像素的平均值並將其寫入輸出文件。

class Start { 

public static void main (String [] args) throws IOException { 

File input= new File("E:\\input.raw"); 

File output= new File("E:\\output.raw"); 
new Start().resizeImage(input,output,2); 

} 



public void resizeImage(File input, File output, int downScaleFactor) throws IOException { 
      byte[] fileContent= Files.readAllBytes(input.toPath()); 
      FileOutputStream stream= new FileOutputStream(output); 
      int i=0; 
      int j=1; 
      int result=0; 
      for(;i<fileContent.length;i++) 
      { 
       if(j>1){ 
        // skip the records. 
        j--; 
        continue; 
       } 
       else { 
        result = fileContent[i]; 
        for (; j < downScaleFactor; j++) { 
         result = ((result + fileContent[i + j])/2); 
        } 
        j++; 
        stream.write(fileContent[i]); 
       } 
      } 
     stream.close(); 
     } 

} 

以上代碼成功運行，我可以看到輸出文件大小的尺寸減小，但是當我嘗試轉換 輸出文件（原始文件）網上JPG（https://www.iloveimg.com/convert-to-jpg/raw-to-jpg）它給我一個錯誤說，文件已損壞。 我已經從相同的在線工具轉換輸入文件，它完美的工作。我的代碼正在創建損壞的文件有問題。 我該如何糾正它？

P.S我不能使用任何直接縮小圖像的庫。

Answer 1

您的代碼沒有處理圖片大小調整。

請參閱how-to-resize-images-in-java。

哪個，我在這裏複製一個簡單的版本：

import java.awt.Graphics2D; 
import java.awt.image.BufferedImage; 
import java.io.File; 
import java.io.IOException; 

import javax.imageio.ImageIO; 

public class ImageResizer { 

    public static void resize(String inputImagePath, 
      String outputImagePath, int scaledWidth, int scaledHeight) 
      throws IOException { 
     // reads input image 
     File inputFile = new File(inputImagePath); 
     BufferedImage inputImage = ImageIO.read(inputFile); 

     // creates output image 
     BufferedImage outputImage = new BufferedImage(scaledWidth, 
       scaledHeight, inputImage.getType()); 

     // scales the input image to the output image 
     Graphics2D g2d = outputImage.createGraphics(); 
     g2d.drawImage(inputImage, 0, 0, scaledWidth, scaledHeight, null); 
     g2d.dispose(); 

     // extracts extension of output file 
     String formatName = outputImagePath.substring(outputImagePath 
       .lastIndexOf(".") + 1); 

     // writes to output file 
     ImageIO.write(outputImage, formatName, new File(outputImagePath)); 
    } 

    public static void resize(String inputImagePath, 
      String outputImagePath, double percent) throws IOException { 
     File inputFile = new File(inputImagePath); 
     BufferedImage inputImage = ImageIO.read(inputFile); 
     int scaledWidth = (int) (inputImage.getWidth() * percent); 
     int scaledHeight = (int) (inputImage.getHeight() * percent); 
     resize(inputImagePath, outputImagePath, scaledWidth, scaledHeight); 
    } 

    public static void main(String[] args) { 
     String inputImagePath = "resources/snoopy.jpg"; 
     String outputImagePath1 = "target/Puppy_Fixed.jpg"; 
     String outputImagePath2 = "target/Puppy_Smaller.jpg"; 
     String outputImagePath3 = "target/Puppy_Bigger.jpg"; 

     try { 
      // resize to a fixed width (not proportional) 
      int scaledWidth = 1024; 
      int scaledHeight = 768; 
      ImageResizer.resize(inputImagePath, outputImagePath1, scaledWidth, scaledHeight); 

      // resize smaller by 50% 
      double percent = 0.5; 
      ImageResizer.resize(inputImagePath, outputImagePath2, percent); 

      // resize bigger by 50% 
      percent = 1.5; 
      ImageResizer.resize(inputImagePath, outputImagePath3, percent); 

     } catch (IOException ex) { 
      System.out.println("Error resizing the image."); 
      ex.printStackTrace(); 
     } 
    } 

}