1. A Media Computation Cookbook Manipulating Images and Sounds for Use in Alice Part 1: Image Manipulations Part 2: Advanced Image Manipulations, e.g., changing colors in an area Part 3: Chromakey for digital video effects Part 4: Manipulated images with Alice Part 5: Sound manipulations Part 6: Manipulated sounds in Alice

2. Review of code used last time print - prints out the value of whatever variable=Something – sets variable equal to the value of Something. pickAFile() – lets you pick a file, and has a value of the filename you pick. makePicture(filename) – takes a filename as input, and has a value of a Picture object. explore(picture) – shows you the picture. getPixels(picture) – gets a list of all pixels in a picture. for – lets you change one pixel at a time from a list of pixels. getRed/setRed, getBlue/setBlue, getGreen/setGreen – gets or sets the color component of a pixel

3. Functions we did last time def decreaseRed(picture): for p in getPixels(picture): value=getRed(p) setRed(p,value*0.5) def decreaseBlue(picture): for p in getPixels(picture): value=getBlue(p) setBlue(p,value*0.7) def maxBlue(picture): for p in getPixels(picture): setBlue(p,255) def decreaseGreen(picture): for p in getPixels(picture): value=getGreen(p) setGreen(p,value*0.7) def clearRed(picture): for p in getPixels(picture): setRed(p,0)

4. Making a negative image def negative(picture): for p in getPixels(picture): r = getRed(p) b = getBlue(p) g = getGreen(p) color = makeColor(255-r, 255-g, 255-b) setColor(p,color) How to use it: >>> picture = makePicture(pickAFile()) >>> negative(picture) >>> writePictureTo(picture,"c:/negativepic.jpg")

5. Some new pieces of code makeColor(redamount, greenamount, blueamount) – makes a new color. setColor(pixel,color) – sets a color of a pixel. getColor(pixel) – has a value of the color of the pixel

6. What happens if…? You do negative twice? You clear out a color (red, green, or blue) and then do the negative? (You can have many explore windows open at once, so you can compare them.)

7. How do you get grayscale? def grayscale(picture): for p in getPixels(picture): r = getRed(p) b = getBlue(p) g = getGreen(p) brightness = ??? color = makeColor(brightness,brightness,brightness) setColor(p,color)

8. Changing just some colors How do we do it? ◦ We have to figure out which pixels to change. ◦ We want pixels that are close to a given color. ◦ We want only those within a certain range

9. What color shirt? Where is it? Y=210 X=220 X=400 >>> shirt = makePicture(pickAFile()) >>> explore(shirt) >>> print shirt Picture, filename C:\mediasources\IMG_0808.JP G height 480 width 640

10. distance() function tells how close colors are >>> print white color r=255 g=255 b=255 >>> print black color r=0 g=0 b=0 >>> print distance(white,black) 441.6729559300637 >>> print red color r=255 g=0 b=0 >>> print pink color r=255 g=175 b=175 >>> print distance(red,pink) 247.48737341529164

11. Changing the whole shirt def changeAllShirt(picture): myGreen = makeColor(132,240,204) for pixel in getPixels(picture): color = getColor(pixel) if distance(color,myGreen) < 200: setColor(pixel,pink)

12. Results

13. Just doing part of the picture, and changing fewer pixels def changeShirt(picture): myGreen = makeColor(132,240,204) for x in range(220,400): for y in range(210,480): pixel = getPixel(picture,x,y) color = getColor(pixel) if distance(color,myGreen) < 50: setColor(pixel,pink)

14. Results

15. Coloring the shirt from a different picture >>> beach = makePicture(pickAFile()) >>> shirt = makePicture(pickAFile())

16. Code to grab other colors def newBackgroundShirt(picture,background): myGreen = makeColor(132,240,204) for x in range(220,400): for y in range(210,480): pixel = getPixel(picture,x,y) color = getColor(pixel) if distance(color,myGreen) < 100: backgroundPixel = getPixel(background,x,y) backgroundColor = getColor(backgroundPixel) setColor(pixel,backgroundColor)

17. Results

18. Try it! Get the shirt to turn pink really well Change something else: ◦ Make a yellow or red shirt different colors ◦ Change the white of someone’s teeth to green Change someone else’s shirt into a different background. Real Challenge: Save a picture from Alice, and then change colors in that picture!