Hello Python Tutors!
I am a non-computer science major taking a computer programming course. That
is the first red flag you should know. Second red flag, the course is poorly, I
mean poorly written. third red flag, it is a distance education course, so it
is done online. Needless to say I am in big trouble. I have been working on
this assignment for days and have gotten nowhere. here are the directions:
For this assignment, you will create a web script that lets the user explore
RGB colours.
On the first page the user sees, they should specify two RGB colours. When they
submit this page, they should be presented with a range of colours in between
the two. The intermediate colours will be calculated by your program.
For example, if the user enters the colours red (100% red, 0% green, 0% blue)
and white (100% red, 100% green, 100% blue), your program might output a page
containing this:
(image of a color box)
If you want, you can experiment with an example of a working colour explorer.
You can copy HTML and CSS code from this example if you wish.
The easiest way to create one of the blocks of colour is with a <div> like
this:
<div class="colourblock" style="background-color: rgb(100.0%,50.0%,0.0%)">
</div>
There are a couple of new things here. First, note that you can indicate style
information with the style attribute on an HTML tag. This is generally a bad
idea, but it's possible for cases just like this where you want to control the
style of individual elements in very specific ways.
Second, you can specify an RGB colour in CSS by specifying three percentages as
in rgb(100%, 50%, 0%). This isn't used as commonly as the hexadecimal method
we've used in the course up to now, but it is supported by modern web browsers
and will be much easier to work with in our program. In this example, the
colour will have a lot of red (100%=F), half green (50%≅7) and no blue (0%=0)
Here's how you calculate the in-between colours: I'm going to assume the
percentage of red the user specified for the first colour is an integer in red1
and the amount of red for colour two is in red2. The number of steps the user
requested is in nsteps. If you want the amount of red (as a percent) for colour
block i, you can do this (assuming i goes from 0 to nsteps-1):
fraction = (i+1.0)/nsteps
r = (1-fraction)*red1 + fraction*red2
After this, the variable r will contain the correct percent (as a floating
point value). The calculation for green and blue are exactly the same. (You
don't have to repeat the calculation of fraction, of course.)
Here are some other points about how the program should behave:
• You will have to apply a style sheet to the <div> tags so they are
large enough to see. Something like this might be appropriate:
colourblock { width: 10em; height: 1em; }
• Your program must never output more than 150 total colours, no matter
how many the user asks for. If the users asks for more, it should only output
150.
Having a limitation like this is an essential security measure. If not, someone
could ask for 1000000 steps; this would overload the server and someone would
probably come asking you why you used so much of the University's bandwidth.
[Actually, the course web server automatically limits the size of the page your
script can create. This isn't the case on most web servers so you should get
into the habit of paying attention to the amount of output you generate. Python
scripts on the server are limited to 60k of output.]
• You don't have to worry about catching errors in the user's input. That
is, don't worry about the possibility of them entering "abcd" as the number of
steps.
• You have to be careful about the spacing when outputting the RGB
percentage values. You will have to convert the numbers to strings and
concatenate them. For example, this statement will output part of the style
attribute:
print 'style="background-color: rgb(' + str(r) + '%'
• All of your XHTML (including generated XHTML) and CSS must be valid.
I have no idea how to begin!! can you help me?
Thank you,
Andrea Semenik
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