Q.1
When we processed each pixel, the picture changed top-first then down to the bottom. When we use the index number, we processed:
Top-first then down to the bottom
Bottom-first up to the top
Left to right
Right to left
Q.2
Which of these tasks would be easier when processing pictures by index number?
Making a grayscale image
Negating the image
Zeroing out all red channel values
Change the color of every third pixel