$10.$ Add Sepia Conversion

Sepia was a process used to increase the longevity of photographic prints. To simulate a sepia$-$toned photograph, you darken the green value to int$(0\mathrm{.}6*$ brightness$)$ and blue value to int$(0\mathrm{.}4*$ brightness$),$ producing a reddish$-$brown tone. Extend your implementation of mono to include the case when sepia is True. Use an if$-$statement to make sure that you do not break grayscale conversion. Your function should produce normal grayscale when sepia is False and sepia tone when it is True.

To test out sepia tone, you will need to execute pictool.py with the sepia option, adding $--$sepia$=$True to the end of the command line. For example, executing the command

python pictool.py mono images$/$Walker$.$png Walker$2.$png $--$sepia$=$True

should perform the following conversion:

# IMPLEMENT THESE FOUR FUNCTIONS

def mono$($image$,$ sepia$=$False$)$:

$"""$

Returns True after converting the image to monochrome.

All plug$-$in functions must return True or False. This function returns True

because it modifies the image. It converts the image to either greyscale or

sepia tone, depending on the parameter sepia.

If sepia is False, then this function uses greyscale. For each pixel, it computes

the overall brightness, defined as

$0\mathrm{.}3*$ red $+0\mathrm{.}6*$ green $+0\mathrm{.}1*$ blue.

It then sets all three color components of the pixel to that value. The alpha value

should remain untouched.

If sepia is True, it makes the same computations as before but sets green to

$0\mathrm{.}6*$ brightness and blue to $0\mathrm{.}4*$ brightness.

Parameter image: The image buffer

Precondition: image is a $2$d table of RGB objects

Parameter sepia: Whether to use sepia tone instead of greyscale

Precondition: sepia is a bool

$"""$

# We recommend enforcing the precondition for sepia

# Change this to return True when the function is implemented

assert type$($sepia$)$ is bool

height $=$ len$($image$)$

width $=$ len$($image$[0])$

for row in range$($height$)$:

for col in range$($width$)$:

pixel $=$ image$[$row$][$col$]$

brightness $=0\mathrm{.}3*$ pixel.red $+0\mathrm{.}6*$ pixel.green $+0\mathrm{.}1*$ pixel.blue

pixel.red $=$ int$($brightness$)$

if sepia:

pixel.green $=$ int$($brightness $*0\mathrm{.}6)$

pixel.blue $=$ int$($brightness $*0\mathrm{.}4)$

else:

pixel.green $=$ pixel.red

pixel.blue $=$ pixel.red

return True