Color[][] is not storing color. Object reference not set to an instance of an object.

Question

Hello, I am trying to reverse an image of a texture2D. I have tried many different attempts at this problem to no avail (including, but not limited to: Reverse() of arraylist, mixing jagged arrays, and looping through individual pixels). Here is a snippet of code for the reverse function.

 void ReverseImageX(Texture2D image)
     {
         //Get the array ready
         Color[][] newColorArrayWidth = new Color[image.height][];
 
         //Deconstruct the picture and get every pixel
         for(int i = 0; i < image.height; i++)
         {
             //Get the width of the picture
             for(int j = image.width - 1; j >= 0; j--)
             {
                 newColorArrayWidth[i][j] = image.GetPixel(j, i); //Error here: NullReferenceException: Object reference not set to an instance of an object
             }
         }
 
         //Reconstruct the picture reveresed in the X-axis
         for(int i = 0; i < image.height; i++)
         {
             //use the width of the picture to reconstruct the image
             for(int j = 0; j > image.width; j++)
             {
                 //Reconstruct
                 image.SetPixel(j, i, newColorArrayWidth[i][j]);
             }
         }
     }

I am also trying to not only reverse the image horizontally, but also vertically. But I assume that it is just messing with the for loops to get that desired effect.

The error is happening on line 364 (in this case it is: "newColorArrayWidth[i][j] = image.GetPixel(j, i);") and is not storing the color in the multidimensional array. I know this function is working by reciving the image through the parameter and going through the loop conditions, but stops at that line.

Answer 1

Best Answer

Answer by code_warrior · Jan 12, 2015 at 11:08 AM

The enclosed function shows an easier way to flip a texture horizontally and vertically.

 Texture2D FlipTexture(Texture2D original){
            Texture2D flipped = new Texture2D(original.width,original.height);
            int xN = original.width;
            int yN = original.height;
            for(int i=0;i<xN;i++){
               for(int j=0;j<yN;j++){
                   flipped.SetPixel(xN-i-1, yN-j-1, original.GetPixel(i,j));
               }
             }
     flipped.Apply();
     return flipped;
 }

Note code is not tested code_warrior

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AmasterAmaster · Jan 12, 2015 at 12:45 PM 0

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Alright, this works, but it flips it vertically (And I am happy it is at least flipping). Is there any advice you can give that would help me flip this horizontally? (I imaging that I may have to switch the for loops or switch the algorithm while setting the pixel). And thank you again for helping me with this problem.

Answer 2

Answer by zharik86 · Jan 12, 2015 at 08:07 AM

For multidemention array use:

  void ReverseImageX(Texture2D image) {
   //Get the array ready
   //Create right multidemention array
   Color[ , ] newColorArrayWidth = new Color[image.height, image.width];
 
   //Deconstruct the picture and get every pixel
   
   for(int i = 0; i < image.height; i++) {
    //Get the width of the picture
    for(int j = image.width - 1; j >= 0; j--) {
     //In your case newColorArrayWidth[i][j] is not always GetPixel(j, i), only square picture
     newColorArrayWidth[image.width - 1 - j , i] = image.GetPixel(j, i); //get right colors and position into array
    }
   }

   //Reconstruct the picture reveresed in the X-axis
   for(int i = 0; i < image.height; i++) {
    //use the width of the picture to reconstruct the image
    for(int j = 0; j > image.width; j++) {
     //Reconstruct
     image.SetPixel(j, i, newColorArrayWidth[j, i]);
    }
   }
   image.Apply(); //apply to memory
  }

I hope that it will help you.

P.S.: If you want use array[][], than you must initialization it:

  Color[][] newColorArrayWidth = null;
  newColorArrayWidth = new Color[image.height][];
  for(int i = 0; i < image.height; i++) {
   newColorArrayWidth[i] = new Color[image.width];
  }

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AmasterAmaster · Jan 12, 2015 at 09:18 AM 0

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Ok, I will give that a try. I will let you know if it worked out or not.

AmasterAmaster · Jan 12, 2015 at 12:41 PM 0

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Ok, I have tried this (as well as mixing and matching some arrays around) and it did get rid of the error I was having (thank you very much). But when I ran it, it did nothing to flip the texture. $$anonymous$$aybe it had something to do with the logic I was messing with, but thank you for enlightening me on the array problem.

zharik86 · Jan 13, 2015 at 07:18 AM 0

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@AmasterAmaster After change pixels you must apply texture to memory. I add it to my answer.

AmasterAmaster · Jan 14, 2015 at 10:04 AM 0

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Ok, and thanks again for the help, only if messing with textures were as simple as messing with game objects (when thinking in a higher level: scaling backwards), but I see that it is not that simple for this game engine when it comes to pixels. I do appreciate the help.

Color[][] is not storing color. Object reference not set to an instance of an object.

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