{
"nbformat": 4,
"nbformat_minor": 0,
"metadata": {
"colab": {
"provenance": []
},
"kernelspec": {
"name": "python3",
"display_name": "Python 3"
},
"language_info": {
"name": "python"
}
},
"cells": [
{
"cell_type": "markdown",
"source": [
"**Name:**\n",
"\n",
"**Date:**\n",
"\n",
"**Description of activity:**\n"
],
"metadata": {
"id": "sczaGya92i48"
}
},
{
"cell_type": "markdown",
"source": [
"# Mount Google Drive\n"
],
"metadata": {
"id": "mv3Oarmb2zRK"
}
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"id": "1i3bvglG2d8z"
},
"outputs": [],
"source": [
"from google.colab import drive\n",
"drive.mount('/drive')"
]
},
{
"cell_type": "markdown",
"source": [
"# Import Libraries"
],
"metadata": {
"id": "GXNipdi-3F1Z"
}
},
{
"cell_type": "code",
"source": [
"from PIL import Image\n",
"from matplotlib import pyplot as plt"
],
"metadata": {
"id": "8Nmg8IhE3KfV"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"# Exercises\n",
"\n",
"In this activity you will gain practice defining your own functions and using if statements (conditional statements) in Python to manipulate pixels to create different effects on images.\n",
"\n"
],
"metadata": {
"id": "MJ8VoPpTy-mD"
}
},
{
"cell_type": "markdown",
"source": [
"**Coloring portions of pictures using conditional statements**\n",
"\n",
"In a previous activity we saw how we could use ranges of for loops with different start, end, and step values to specify which pixels in an image to change. We will now see how we can do this with if statements.\n",
"\n",
"The following function changes the color of the top half of an image to be red. Load it and test it."
],
"metadata": {
"id": "FbBK1CL0Qk5F"
}
},
{
"cell_type": "code",
"source": [
"# Color top left quadrant red\n",
"def topHalfRed(picture):\n",
" newPic = picture.copy()\n",
"\n",
" for y in range(newPic.height):\n",
" for x in range(newPic.width):\n",
" if (y < newPic.height/2):\n",
" newPic.putpixel((x,y),(255,0,0))\n",
"\n",
" return newPic"
],
"metadata": {
"id": "m3yexlvARUeL"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "code",
"source": [
"# Test topHalfRed function here\n",
"\n"
],
"metadata": {
"id": "YqNtfobFT9Pe"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"**Coloring Other Sections**\n",
"\n",
"Define three new functions to change the color of pixels in the specified sections of an image. Each of these functions should loop through all of the pixels in an image and use appropriate expressions in an if statement to select the pixels that will get changed.\n",
"\n",
"\n",
"1. colorLeftHalf: Color left half a specified color.\n",
"2. colorTopLeft: Color top left quadrant a specified color.\n",
"3. (Optional, if time permits) colorBottomRight: Color bottom right quadrant a specified color.\n",
"4. (Optional, if time permits) middleQuadrant: Color the middle quadrant a specified color. This will take a little more thinking to figure out what *x*- and *y*- values you will need.\n",
"\n"
],
"metadata": {
"id": "PQ1IroKpSWxA"
}
},
{
"cell_type": "code",
"source": [
"# Define your new functions here.\n",
"\n",
"\n"
],
"metadata": {
"id": "C-XFu7nPTiWx"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"**(OPTIONAL, IF TIME PERMITS) Drawing every other line**\n",
"\n",
"Think about how you might use conditional statements to draw every other line horizontally or vertically. What coodinates do you need to use? For example, if you wanted to draw every other line horizontally on a 100x50 image, you would select all of the pixels in row 0, then in row 2, then in row 4, etc. This would give us the pixels (0, 0), (1, 0), (2, 0), ... (199, 0), (0,2), (1, 2), (3, 2), ...(199, 2), ... (0, 48), (1, 48), ..., (199, 48). Notice that the y-value of each of these pixels is even. One way to check if a number is even is to use the mod operator (%), as it gives the remainder of division. So an expression such as y % 2 would return 0 for even numbers and 1 for odd numbers. (Why?)\n",
"Define an everyOther function that draws every other horizontal or vertical lines in an image by looping through all of the pixels and using an if statement to select the ones to be changed."
],
"metadata": {
"id": "KsG59zoEXG8V"
}
},
{
"cell_type": "code",
"source": [
"# Define and test your function here\n",
"\n"
],
"metadata": {
"id": "5hahZTEZZEqN"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"**Draw a diagonal line**\n",
"\n",
"The Conditional Statements reading explains how to draw a diagonal line from the top left corner of a square image to the bottom right corner by changing the color of the pixels along the diagonal. These are the pixels (0,0), (1,1), (2, 2), etc. The following function will do this by using an if statement to check if the *x*- and *y*- values are the same. Load this function and test to see how it works on a **square** image. Then test to see what line it draws on images that are not square. What line does it draw?"
],
"metadata": {
"id": "nGwjr7geUnfB"
}
},
{
"cell_type": "code",
"source": [
"# This function draws a diagonal line on an image\n",
"def drawDiagonal(picture):\n",
" newPic = picture.copy()\n",
"\n",
" for y in range(newPic.height):\n",
" for x in range(newPic.width):\n",
" if x == y:\n",
" newPic.putpixel((x, y), (255, 0, 0))\n",
"\n",
" return newPic"
],
"metadata": {
"id": "8WMLzD5bAQxP"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "code",
"source": [
"# Test your diagonal function here on square and non-square images\n",
"\n"
],
"metadata": {
"id": "w0XxuuTsCnEP"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"**Tint Red**\n",
"\n",
"We can now explore how to use if statements to select color values that we wish to change. The following function is from the [Conditonal Statements reading](http://www.cs.kzoo.edu/cs103/Readings/ConditionalStatements.pdf) and will increase the red by 150% for pixels that originally had a small amount of red. Copy and load this function and then test it. Experiment with changing the factor for how much the red changes and/or which values of red you'd like to change.\n",
"\n"
],
"metadata": {
"id": "ahvRleAABi5s"
}
},
{
"cell_type": "code",
"source": [
"# Copy the tintRed function here\n",
"\n",
"\n",
"\n"
],
"metadata": {
"id": "peXqXT_jCcX-"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"Test that this function behaves like we think it should. Show the original image side-by-side with the reflected image."
],
"metadata": {
"id": "a92yyIooCzeW"
}
},
{
"cell_type": "code",
"source": [
"# Test tintRed function here\n",
"\n",
"\n"
],
"metadata": {
"id": "FOgwUiHNzInJ"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"**Doubling and Halving**\n",
"\n",
"Define a new function, doubleHalf that changes the amount of red in an image by doubling any red value that is less than 127 and halving any red value that is greater than 127. Your function should use an if-else statement to check the red value.\n"
],
"metadata": {
"id": "D4XRNj0yKQJ-"
}
},
{
"cell_type": "code",
"source": [
"# Define your function here\n",
"\n"
],
"metadata": {
"id": "G1vZd-zYZOpa"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "code",
"source": [
"# Test your doubleHalf function here\n",
"\n"
],
"metadata": {
"id": "KkDVs_ZsZTAP"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"**Modify doubleHalf**\n",
"\n",
"Modify the doubleHalf function so that it also modifies the green and blue values similar to the modification of red values. Test your modified function."
],
"metadata": {
"id": "nchG5KCOLHlC"
}
},
{
"cell_type": "code",
"source": [],
"metadata": {
"id": "Hm1gu7iiKPQl"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"**Color switching** \n",
"\n",
"We will now experiment with swapping one color for another color. Define a new function, colorSwitch that will take an image and a new color (defined as a 3-tuple for R, G, B) as parameters, and returns a new version of the image with the new color replacing the red in the image.\n",
"In the images below, the red from the flowers was replaced with an aqua color. To do this, the function needs to kwow what values make up red. Pure red is (255, 0, 0). It is unlikely that the image has pure red pixels. After experimenting a little, it was determined that if the red value of a pixel is > 175, the green value is < 100 and the blue value is also < 100, then that pixel is a shade of red. That pixel then got replaced with a shade of aqua (20, 200, 180).\n",
"Your function should duplicate the original picture, and then loop through all of the pixels in the copy, checking if the RGB values of the pixel meet the criteria you desire. Change the color values for any pixel that meets this criteria.\n",
"\n"
],
"metadata": {
"id": "lGhTaVgZ0AHx"
}
},
{
"cell_type": "markdown",
"source": [
"**Experiment with sepia tint and posterize**\n",
"\n",
"Copy the sepiaTint, the simplePosterize and the posterize functions from the [Conditional Statements reading ](http://www.cs.kzoo.edu/cs103/Readings/ConditionalStatements.pdf) and test them. Show your results."
],
"metadata": {
"id": "sgDLeqxCDxDQ"
}
},
{
"cell_type": "code",
"source": [
"# Sepia, Posterize functions here\n",
"\n",
"\n"
],
"metadata": {
"id": "oZOPsFs6mGj9"
},
"execution_count": null,
"outputs": []
},
{
"cell_type": "markdown",
"source": [
"# Saving and Submitting\n",
"\n",
"Once you have created results that you are pleased with, skim through your notebook and make sure everything looks the way you expect. If it all looks good, save this notebook as a .ipynb file. (Go to File -> Download -> Download .ipynb)\n",
"\n",
"Submit your .ipynb file on Kit."
],
"metadata": {
"id": "m8jTI0_OBDRM"
}
}
]
}