FAQs on the exercise Combining Traversal and Conditional Logic
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newImage would be a 2D array of ints (meaning newImage is an array of arrays of integers);
so the stuff inside newImage are arrays.
In the code posted, you tried to subtract 50 from an array, which creates an error.
To fix that, you can have an outer loop that iterates through the arrays of integers, and an inner loop that iterates through the integers.
Yea, I think that inner lop made a copy of the values, and changed that copy instead of changing the original integers.
I guess the inner loop should iterate using the index instead.
Could you tell me please why it doesn’t work? I know the task could be achieved simpler, but I wanted to use the Math.abs() method. I imported the library correctly (import static java.lang.Math.*; )
Single nested for loop solution for steps 2 & 3. It seems like it might be easy to miss that, having already defined the parameters of the newImage 2D array, performing math or having an extra conditional in the for loop using the bounds of the imageData 2D array is unnecessary.
Instead of iterating through the 8 columns of imageData and using a conditional to ignore the last two, we can use the defined 6 rows of the newImage 2D array to automatically stop after six items when copying from each sub-array.
And since we are already iterating through, we can alter each value of the inner array as we copy it over to the newImage
import java.util.Arrays;
public class Combining {
public static void main(String args) {
int imageData={{100,90,255,80,70,255,60,50},
{255,10,5,255,10,5,255,255},
{255,255,255,0,255,255,255,75},
{255,60,30,0,30,60,255,255}};
//First, we want to crop the image down to a 4x6 image, removing the right 2 columns. Declare and initialize a new 2D array of integers with 4 rows and 6 columns called `newImage`.
int[][] newImage = new int[4][6];
for (int i=0; i<imageData[0].length && i<6; i++) {
for (int j =0; j<imageData.length; j++) {
newImage[j][i] = imageData[j][i];
}
}
//Now that you have your empty image, use nested **for** loops to copy over the data from the original image to the new image, make sure not to include the cropped out columns.
System.out.println(Arrays.deepToString(newImage));
//You want to decrease the brightness of the new image by 50 units. The way this works is that for every integer in the new 2D array, we will subtract the value by 50. Remember that the value range for the pixel is 0-255, so if the result tries to go below 0, just set it equal to 0.
for (int[] row: newImage) {
for (int j=0; j<row.length; j++) {
if (row[j] - 50 < 0 ) {
row[j] = 0;
} else {
row [j] -= 50;
}
}
}
System.out.println(Arrays.deepToString(newImage));
}
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