从文本文件获取的字符数组：索引超出范围

我正在编写一个程序，以接收包含三个不同字符的50 x 50块的文本文件的输入：＃，*和/，并根据每个符号为输出PNG文件的每个像素着色，以便有一个与每个字符相关的颜色。

但是，我在第43行看到“字符串索引超出范围：2500”的错误。

我知道虽然正在读取的文本文件正好有50行，每行50个字符，这意味着总共有2500个项目，那么问题是什么呢？帮助将不胜感激。

这是我的代码：

import java.util.Scanner;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter; 

public class Lab_Week8_ImgFrmTxtFINAL {

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

    int image_width = 50;
    int image_height = 50;
    String output_file_path = ("image.png");
    String input_file_path = "superimage.txt";
    int r = 0;
    int g = 0;
    int b = 0;
    int a = 255;
    Scanner reader = new Scanner (new FileInputStream(input_file_path));
    int i = 0;
    int x = 0;
    int y = 0; 


    if(image_width <= 0 || image_height <= 0) {
        System.err.println("Width and Height have to be strictly positive!");
    }

    if(x < 0 || y < 0) {
        System.err.println("Coordinates (x, y) cannot be negative numbers!");
    }

    if(r < 0 || r > 255 || g < 0 || g > 255 || b < 0 || b > 255) {
        System.err.println("Colour values (r, g, b) have to be between 0 and 255!");
        }   

    BufferedImage image = new BufferedImage (image_width, image_height, BufferedImage.TYPE_INT_ARGB);

    while (reader.hasNextLine()){
        char c = reader.next().charAt(i);
        for (i = 0; i < image_width * image_height; i++)
        {

        int p = (a << 24) | (r << 16) | (g << 8) | b;

        for (x = 0; x < image_width; x++)
        {
            for (y = 0; y < image_height; y++){

                if (c == ('#'))
                {p = (a << 24) | (r << 16) | (g << 8) | b;
                image.setRGB(x, y, p);
                }

                else if (c == ('/'))
                {p = (a << 0) | (r << 16) | (g << 8) | b;
                    image.setRGB(x , y , p);
                }

                else if (c == ('*'))
                {p = (a << 8) | (r << 16) | (g << 24) | b;
                    image.setRGB(x , y , p);
                }
            }   
        x += 1;
    }
    y += 1;
    x = 0;
    }

    }
    File f = new File (output_file_path);
    ImageIO.write(image, "png", f);

    reader.close();
}
}