swaping和旋轉2D陣列

Question

我需要實現兩種方法，用二維數組工作：

• grayAndFlipLeftToRight - 該方法將圖像轉換成灰度值的2D陣列，然後將其翻轉左到右。也就是說，面向左的對象現在將面向右。最左列的元素將與最右列的元素交換，依此類推。

• grayAndRotate90 - 此方法將圖像轉換爲二維灰度值數組，然後順時針旋轉90度（將其放置在右側）。

代碼：

public class PictureUtil 
{ 
    /** 
    * Gets a version of the given Picture in gray scale and flipped left to right 
    * @param pic the Picture to convert to gray scale and flip 
    * @return a version of the original Picture in gray scale and flipped 
    * left to right. 
    */ 
    public static Picture grayAndFlipLeftToRight(Picture pic) 
    { 
     int[][] pixels = pic.getGrayLevels(); 

     for (int i = 0; i < pixels.length; i++) {    
      for (int fromStart = 0; fromStart < pixels[0].length; fromStart++) { 
       int fromEnd = pixels[0].length-1; 

       while (fromEnd >= 0) { 
        int saved = pixels[i][fromStart]; 
        pixels[i][fromStart] = pixels[i][fromEnd]; 
        pixels[i][fromEnd] = saved; 

        fromEnd--; 
       }            
      } 
     } 

     return new Picture(pixels); 
    } 

    /** 
    * Gets a version of the given Picture in gray scale and rotated 90 degrees clockwise 
    * @param pic the Picture to convert to gray scale and rotate 90 degrees clockwise 
    * @return a version of the original Picture in gray scale and rotated 90 degrees clockwise 
    */ 
    public static Picture grayAndRotate90(Picture pic) 
    { 
     int[][] pixels = pic.getGrayLevels(); 

     int numberOfColums = pixels.length; 
     int numberOfRows = pixels[0].length;   
     int[][] rotate = new int[numberOfRows][numberOfColums]; 

     for (int i = 0; i < pixels.length; i++) { 
      int seek = 0; 
      for (int j = 0; j < pixels[0].length; j++) {    
       pixels[i][j] = rotate[seek][numberOfColums - 1]; 
       seek++; 
      } 
     } 

     return new Picture(rotate); 
    } 
} 

我的實現不正確兩種方法的工作。

• 如何解決這個問題？

Answer 1

我覺得你搞砸了循環了一下。這應該讓您的工作：

public static Picture grayAndFlipLeftToRight(Picture pic) 
{ 
    int[][] pixels = pic.getGrayLevels(); 

    for (int i = 0; i < pixels.length; i++) { 
     for (int curr = 0; curr < (pixels[0].length + 1)/2; curr++) { 

      int saved = pixels[i][curr]; 
      pixels[i][curr] = pixels[i][pixels[0].length - 1 - curr]; 
      pixels[i][pixels[0].length - 1 - curr] = saved; 
     } 
    } 

    return new Picture(pixels); 
} 

public static Picture grayAndRotate90(Picture pic) 
{ 
    int[][] pixels = pic.getGrayLevels(); 

    int[][] rotate = new int[pixels[0].length][pixels.length]; 

    for (int i = 0; i < pixels[0].length; i++) { 
     for (int j = 0; j < pixels.length; j++) { 
      rotate[i][pixels.length - 1 - j] = pixels[j][i]; 
     } 
    } 
    return new Picture(rotate); 
} 

代碼中的錯誤是（在旋轉法）行：

pixels[i][j] = rotate[seek][numberOfColums - 1]; 

您要修改輸入數組本身的內容，並與旋轉無所事事輸出爲。

Answer 2

有趣的是，如果你想逆時針旋轉90的代碼如下所示：

public static Picture grayAndRotate90CC(Picture pic) 
{ 
    int[][] pixels = pic.getGrayLevels(); 

    int[][] rotateCC = new int[pixels[0].length][pixels.length]; 

    for (int i = 0; i < pixels[0].length; i++) { 
     for (int j = 0; j < pixels.length; j++) { 
      rotateCC[i][j] = pixels[j][i]; //rotates 90 counter-clockwise! 
     } 
    } 
    return new Picture(rotateCC); 
}