1 / 41

CS1315: Introduction to Media Computation

CS1315: Introduction to Media Computation. Programming picture manipulations Goofing around with pictures. Administrivia. Grades will be available via WebWork Demo Lab 2 due this Friday Lab 3 due date is soon! Monday, August 30 th Does everyone have JES installed now?.

nansen
Download Presentation

CS1315: Introduction to Media Computation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CS1315:Introduction to Media Computation Programming picture manipulations Goofing around with pictures

  2. Administrivia • Grades will be available via WebWork • Demo • Lab 2 due this Friday • Lab 3 due date is soon! • Monday, August 30th • Does everyone have JES installed now?

  3. New Jython and JES Functionsfor this Breakout… (Bingo?) • getPixel, setPixel • getRed/Blue/Green setRed/Blue/Green • getColor, setColor • makeColor • pickAColor • makeDarker, makeLighter • distance • for

  4. Exploring Pictures • >>> aPic = makePicture(pickAFile()) • MediaTools -> Picture Tool… • Choose picture to investigate • Click and drag to get pixel values, positions • Select “Update Picture… -> Update” after you make changes to the picture • What are RGB values for a red pixel in the picture? • For a yellow pixel? • For orange?

  5. Getting at Pixels in Code • >>> samplePixel = getPixel(aPic, 100, 100) • >>> print samplePixelPixel, color=color r=235 g=126 b=5 • What can we do with a pixel once we get it?

  6. Pixel Colors • >>> print getColor(samplePixel)color r=235 g=126 b=5 • >>> print getRed(samplePixel)235 • >>> print getGreen(samplePixel)126 • >>> print getBlue(samplePixel)5

  7. How Do We Set the Color? • We get the pixel colors by calling getRed(…) getGreen(…) or getBlue(…) • How do we set the colors?

  8. setRed(), setGreen(), setBlue() • >>> setRed(samplePixel, 0) • >>> setGreen(samplePixel, 0) • >>> setBlue(samplePixel, 255) • Choose “Update” in Media Tools to see differences in Media Tools window • Update pictures shown with “show” with “repaint” • >>> repaint(aPic)

  9. More Colors • >>> thisColor = makeColor(0, 0, 255) • >>> samplePixel = getPixel(aPic, 100, 101) • >>> setColor(samplePixel, thisColor) • Choose “Update” in Media Tools to see diff • >>> print getColor(samplePixel) • >>> newColor = pickAColor() • >>> setColor(samplePixel, newColor) • Choose “Update” in Media Tools to see diff

  10. Making Colors Darker or Lighter • >>> aColor = pickAColor()java.awt.Color[r=102,g=102,b=255] • >>> print aColorcolor r=102 g=102 b=255 • >>> makeDarker(aColor) • >>> print aColorcolor r=71 g=71 b=178 • >>> makeLighter(aColor)color r=101 g=101 b=254

  11. Predefined Colors • JES has predefined colors that you can use • blue, yellow, red, green, white… • >>> setColor(samplePixel, blue) • Don’t forget to hit update on Media Tools, or “repaint” for pictures shown with show()

  12. Distance Between Colors • >>> firstColor = pickAColor() • >>> secondColor = pickAColor() • >>> distance(firstColor, secondColor)265.00377355803823 • “distance” is a measure of similarity between two colors • The more similar, the smaller the number • We’ll use this function more at a later date…

  13. Reducing the Tedium • Drawing a blue line… • >>> setColor(getPixel(aPic, 100, 100), blue) • >>> setColor(getPixel(aPic, 101, 100), blue) • >>> setColor(getPixel(aPic, 102, 100), blue) • Works, but is tedious…

  14. Use a loop!Our first picture recipe def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) Used like this: >>> file="/Users/guzdial/mediasources/katie.jpg" >>> picture=makePicture(file) >>> show(picture) >>> decreaseRed(picture) >>> repaint(picture)

  15. How loops are written • for indexVariable in someSequence: doSomething(variableName) … • foris the name of the command • An index variable is used to represent the different values in the loop • The word in • A function that generates a sequence • The index variable will be the name for each value in the sequence, each time through the loop • A colon (“:”) • And, another block

  16. What happens when a loop is executed • The index variable is set to the next (or first, at the beginning) item in the sequence • The block is executed • The variable is often used inside the block • Then execution returns to the top of the for statement, where the index variable gets set to the next item in the sequence • Repeat until the sequence is exhausted

  17. getPixels returns a sequence • getPixels returns a sequence of pixels • Each pixel knows its color and its original picture • Change the pixel, you change the picture • So the loop below assigns the index variable p to each pixel in the picture picture, one at a time def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5)

  18. Do we need value? • Not really: Remember that we can swap names for data or functions that are equivalent. def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) def decreaseRed(picture): for p ingetPixels(picture): setRed(p, getRed(p) *0.5)

  19. Let’s walk that through slowly… Here we get a picture object in as input and call it picture def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) picture

  20. Now, get the pixels We get all the pixels from the picture, then make p be the name of each one one at a time def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) picture getPixels() Pixel, color r=135 g=116b=48 Pixel, color r=133g=114 b=46 Pixel, color r=134 g=114b=45 … p

  21. Get the red value from pixel def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) We get the red value of pixel p and name it value picture getPixels() Pixel, color r=135 g=116b=48 Pixel, color r=133g=114 b=46 Pixel, color r=134 g=114b=45 … … value = 135 p

  22. Now change the pixel def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) Set the red value of pixel p to 0.5 (50%) of value picture getPixels() Pixel, color r=67 g=131 b=105 Pixel, color r=133g=114 b=46 Pixel, color r=134 g=114b=45 … value = 135 p

  23. Then move on to the next pixel def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) Move on to the next pixel and name itp picture getPixels() Pixel, color r=67 g=131 b=105 Pixel, color r=133g=114 b=46 Pixel, color r=134 g=114b=45 … value = 135 p

  24. Get its red value Get its red value def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) Change value to the new red value at the new p picture getPixels() Pixel, color r=67 g=131 b=105 Pixel, color r=133g=114 b=46 Pixel, color r=134 g=114b=45 … value = 133 p p p

  25. And change this red value def decreaseRed(picture): for p ingetPixels(picture): value=getRed(p) setRed(p,value*0.5) Change the red value at pixel p to 50% of value picture getPixels() Pixel, color r=67 g=131 b=105 Pixel, color r=66g=114 b=46 Pixel, color r=134 g=114b=45 … value = 133 p p p

  26. And eventually, we do all pixels • We go from this… to this!

  27. “Tracing/Stepping/Walking through” the program • What we just did is called “stepping” or “walking through” the program • You consider each step of the program, in the order that the computer would execute it • You consider what would specifically happen there • You write down what values each variable (name) has at each point. • It’s one of the most important debugging skills you can have. • And everyone has to do a lot of debugging, especially at first.

  28. Did that really work?How can we be sure? • Sure, the picture looks different, but did we actually decrease the amount of red? By as much as we thought? • Let’s check it!

  29. >>> file = pickAFile() >>> print file C:\Documents and Settings\Mark Guzdial\My Documents\mediasources\barbara.jpg >>> pict = makePicture(file) >>> pixel = getPixel(pict,1,1) >>> print pixel Pixel, color=color r=168 g=131 b=105 >>> decreaseRed(pict) >>> newPixel = getPixel(pict,1,1) >>> print newPixel Pixel, color=color r=84 g=131 b=105 >>> print 168 * 0.5 84.0

  30. Checking it in the MediaTools

  31. If you make something you like… • writePictureTo(picture,”filename”) • Writes the picture out as a JPEG • Be sure to end your filename as “.jpg”! • If you don’t specify a full path,will be saved in the same directory as JES.

  32. Bonus Material • Swap colors • Change Frylock’s color

  33. Swap Colors • Goal: Let’s try to swap the red and blue channels • How to do this?

  34. Swap Colors Code def swapColors(picture): for thisPixel in getPixels(picture): r = getRed(thisPixel) b = getBlue(thisPixel) setBlue(thisPixel, r) setRed(thisPixel, b) repaint(picture)

  35. Change Frylock’s Color • Want to replace Frylock’s color from red to some other color, such as green • Need to test each pixel to see if it is close to Frylock’s color

  36. Testing a Pixel • Need to use a new Jython keyword: if • Example of “if”: if 3 < 5: print “3 is less than 5” • We can check if a pixel is similar to another by using the distance function

  37. Frylock Color Change Code def frylockColorChange(picture): frylockColor = makeColor(224, 45, 49) for pixel in getPixels(picture): thisDistance = distance(frylockColor, getColor(pixel)) if thisDistance < 30: setColor(pixel, green)

  38. Fin

  39. Demonstrating: Manipulating Colors >>> print color color r=81 g=63 b=51 >>> print newcolor color r=255 g=51 b=51 >>> print distance(color,newcolor) 174.41330224498358 >>> print color color r=168 g=131 b=105 >>> print makeDarker(color) color r=117 g=91 b=73 >>> print color color r=117 g=91 b=73 >>> newcolor=pickAColor() >>> print newcolor color r=255 g=51 b=51 >>> print getRed(pixel) 168 >>> setRed(pixel,255) >>> print getRed(pixel) 255 >>> color=getColor(pixel) >>> print color color r=255 g=131 b=105 >>> setColor(pixel,color) >>> newColor=makeColor(0,100,0) >>> print newColor color r=0 g=100 b=0 >>> setColor(pixel,newColor) >>> print getColor(pixel) color r=0 g=100 b=0

  40. We can change pixels directly… >>> file="/Users/guzdial/mediasources/barbara.jpg" >>> pict=makePicture(file) >>> show(pict) >>> setColor(getPixel(pict,10,100),yellow) >>> setColor(getPixel(pict,11,100),yellow) >>> setColor(getPixel(pict,12,100),yellow) >>> setColor(getPixel(pict,13,100),yellow) >>> repaint(pict) But that’s really tedious… Manipulating pictures more cleverly is the next topic…

  41. How do you find out what RGB values you have? And where? • Use the MediaTools! (especially useful when testing and debugging…)

More Related