Copying: How it worksHere's the initial

setup:

Copying: How it works 2After incrementing

the sourceY and targetY once (whether in the for or via expression):

Copying: How it works 3After yet another

increment of sourceY and targetY:

When we finish that column, we increment sourceX and targetX, and start on the next column.

Copying: How it looks at the endEventually, we copy

every pixel

Making a collageCould we do

something to the pictures we copy in? Sure! Could either apply

one of those functions before copying, or do something to the pixels during the copy.

Could we copy more than one picture! Of course! Make a collage!

def createCollage(): flower1=makePicture(getMediaPath("flower1.jpg")) print flower1 flower2=makePicture(getMediaPath("flower2.jpg")) print flower2 canvas=makePicture(getMediaPath("640x480.jpg")) print canvas #First picture, at left edge targetX=0 for sourceX in range(0,getWidth(flower1)): targetY=getHeight(canvas)-getHeight(flower1)-5 for sourceY in range(0,getHeight(flower1)): px=getPixel(flower1,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1 #Second picture, 100 pixels over targetX=100 for sourceX in range(0,getWidth(flower2)): targetY=getHeight(canvas)-getHeight(flower2)-5 for sourceY in range(0,getHeight(flower2)): px=getPixel(flower2,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1

#Third picture, flower1 negated negative(flower1) targetX=200 for sourceX in range(0,getWidth(flower1)): targetY=getHeight(canvas)-getHeight(flower1)-5 for sourceY in range(0,getHeight(flower1)): px=getPixel(flower1,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1 #Fourth picture, flower2 with no blue clearBlue(flower2) targetX=300 for sourceX in range(0,getWidth(flower2)): targetY=getHeight(canvas)-getHeight(flower2)-5 for sourceY in range(0,getHeight(flower2)): px=getPixel(flower2,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1 #Fifth picture, flower1, negated with decreased red decreaseRed(flower1) targetX=400 for sourceX in range(0,getWidth(flower1)): targetY=getHeight(canvas)-getHeight(flower1)-5 for sourceY in range(0,getHeight(flower1)): px=getPixel(flower1,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1 show(canvas) return(canvas)

Page 170-171 (4ed edition)

Can we make that easier?The collage code is

long, yet simple.It's the same thing

over-and-over.We can generalize

that copying loop, and with parameters, use it in many places.

def copy(source, target, targX, targY): targetX = targX for sourceX in

range(0,getWidth(source)): targetY = targY for sourceY in

range(0,getHeight(source)):

px=getPixel(source,sourceX,sourceY) tx=getPixel(target,targetX,targetY) setColor(tx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1

Exact same collage!def createCollage2():

flower1=makePicture(getMediaPath("flower1.jpg"))

print flower1

flower2=makePicture(getMediaPath("flower2.jpg"))

print flower2

canvas=makePicture(getMediaPath("640x480.jpg"))

print canvas #First picture, at left edge

copy(flower1,canvas,0,getHeight(canvas)-getHeight(flower1)-5)

#Second picture, 100 pixels over

copy(flower2,canvas,100,getHeight(canvas)-getHeight(flower2)-5)

#Third picture, flower1 negated negative(flower1)

copy(flower1,canvas,200,getHeight(canvas)-getHeight(flower1)-5)

#Fourth picture, flower2 with no blue clearBlue(flower2)

copy(flower2,canvas,300,getHeight(canvas)-getHeight(flower2)-5)

#Fifth picture, flower1, negated with decreased red

decreaseRed(flower1)

copy(flower1,canvas,400,getHeight(canvas)-getHeight(flower2)-5)

return canvas

Bigger or Smaller?

Does this function make the src bigger or smaller on the canvas?

1.Increases size by 50%

2.Decreases size by 50%

3.Decreases size by 50% and skips some pixels in target

4.Increases size by 50% and skips some pixels in target

>>> c = makePicture("caterpillar.jpg")>>> copyPicDifferent(c,c1,10,10)>>> explore(c1)>>> copyAnyPic(c,c1,10,10)>>> explore(c1)

Transformation = Small changes in copyingMaking relatively small changes in this basic

copying program can make a variety of transformations.Change the targetX and targetY, and you copy

wherever you wantCropping: Change the sourceX and sourceY

range, and you copy only part of the program.Rotating: Swap targetX and targetY, and you

end up copying sidewaysScaling: Change the increment on sourceX

and sourceY, and you either grow or shrink the image.

Copying face to small canvasdef copyHorseFaceSmall(): # Set up the source and target pictures src = makePicture("horse.jpg") canvas = makeEmptyPicture(163,308) # Now, do the actual copying targetX = 0 for sourceX in range(104,267): targetY = 0 for sourceY in range(114,422): color = getColor(getPixel(src,sourceX,sourceY)) setColor(getPixel(canvas,targetX,targetY), color) targetY = targetY + 1 targetX = targetX + 1 show(canvas) return canvas

Changing while copyingdef copyHorseFaceSmallBlack(): hcol = makeColor(216,169,143) # Set up the source and target pictures src = makePicture("horse.jpg") canvas = makeEmptyPicture(163,308) # Now, do the actual copying targetX = 0 for sourceX in range(104,267): targetY = 0 for sourceY in range(114,422): color = getColor(getPixel(src,sourceX,sourceY)) if distance(color,hcol) < 40: setColor(getPixel(canvas,targetX,targetY), black) else: setColor(getPixel(canvas,targetX,targetY), color) targetY = targetY + 1 targetX = targetX + 1 show(canvas) return canvas

Copying vs. Referencing>>> a = 100>>> b = a>>> print a,b100 100>>> b = 200>>> print a,b100 200>>> a = 300>>> print a,b300 200

Referencing works differently>>> pictureBarb = makePicture("barbara.jpg")>>> pixel1 = getPixelAt(pictureBarb,0,0)>>> print pixel1Pixel red=168 green=131 blue=105>>> anotherpixel = pixel1>>> print anotherpixelPixel red=168 green=131 blue=105>>> setColor(pixel1,black)>>> print pixel1Pixel red=0 green=0 blue=0>>> print anotherpixelPixel red=0 green=0 blue=0

Making a collageCould we do

something to the pictures we copy in? Sure! Could either apply

one of those functions before copying, or do something to the pixels during the copy.

Could we copy more than one picture! Of course! Make a collage!

def createCollage(): flower1=makePicture(getMediaPath("flower1.jpg")) print flower1 flower2=makePicture(getMediaPath("flower2.jpg")) print flower2 canvas=makePicture(getMediaPath("640x480.jpg")) print canvas #First picture, at left edge targetX=0 for sourceX in range(0,getWidth(flower1)): targetY=getHeight(canvas)-getHeight(flower1)-5 for sourceY in range(0,getHeight(flower1)): px=getPixel(flower1,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1 #Second picture, 100 pixels over targetX=100 for sourceX in range(0,getWidth(flower2)): targetY=getHeight(canvas)-getHeight(flower2)-5 for sourceY in range(0,getHeight(flower2)): px=getPixel(flower2,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1

#Third picture, flower1 negated negative(flower1) targetX=200 for sourceX in range(0,getWidth(flower1)): targetY=getHeight(canvas)-getHeight(flower1)-5 for sourceY in range(0,getHeight(flower1)): px=getPixel(flower1,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1 #Fourth picture, flower2 with no blue clearBlue(flower2) targetX=300 for sourceX in range(0,getWidth(flower2)): targetY=getHeight(canvas)-getHeight(flower2)-5 for sourceY in range(0,getHeight(flower2)): px=getPixel(flower2,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1 #Fifth picture, flower1, negated with decreased red decreaseRed(flower1) targetX=400 for sourceX in range(0,getWidth(flower1)): targetY=getHeight(canvas)-getHeight(flower1)-5 for sourceY in range(0,getHeight(flower1)): px=getPixel(flower1,sourceX,sourceY) cx=getPixel(canvas,targetX,targetY) setColor(cx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1 show(canvas) return(canvas)

Page 91-92 (2ed edition)

Can we make that easier?The collage code is

long, yet simple.It's the same thing

over-and-over.We can generalize

that copying loop, and with parameters, use it in many places.

def copy(source, target, targX, targY): targetX = targX for sourceX in

range(0,getWidth(source)): targetY = targY for sourceY in

range(0,getHeight(source)):

px=getPixel(source,sourceX,sourceY) tx=getPixel(target,targetX,targetY) setColor(tx,getColor(px)) targetY=targetY + 1 targetX=targetX + 1

Exact same collage!def createCollage2():

flower1=makePicture(getMediaPath("flower1.jpg"))

print flower1

flower2=makePicture(getMediaPath("flower2.jpg"))

print flower2

canvas=makePicture(getMediaPath("640x480.jpg"))

print canvas #First picture, at left edge

copy(flower1,canvas,0,getHeight(canvas)-getHeight(flower1)-5)

#Second picture, 100 pixels over

copy(flower2,canvas,100,getHeight(canvas)-getHeight(flower2)-5)

#Third picture, flower1 negated negative(flower1)

copy(flower1,canvas,200,getHeight(canvas)-getHeight(flower1)-5)

#Fourth picture, flower2 with no blue clearBlue(flower2)

copy(flower2,canvas,300,getHeight(canvas)-getHeight(flower2)-5)

#Fifth picture, flower1, negated with decreased red

decreaseRed(flower1)

copy(flower1,canvas,400,getHeight(canvas)-getHeight(flower2)-5)

return canvas

Rotating the copydef flipHorseSideways(): # Set up the source and target pictures src = makePicture("horse.jpg") canvas = makeEmptyPicture(1000,1000) # Now, do the actual copying targetX = 0 for sourceX in range(0,getWidth(src)): targetY = 0 for sourceY in range(0,getHeight(src)): color = getColor(getPixel(src,sourceX,sourceY)) # Change is here setColor(getPixel(canvas,targetY,targetX), color) targetY = targetY + 1 targetX = targetX + 1 show(canvas) return canvas

Rotating: How it worksWe increment the

same, but we use targetX for the Y coordinate and targetY for the X coordinate

Rotate: How it endsSame amount of

increment, even same values in the variables, but a different result.

Doing a real rotation

def rotateHorseSideways(): # Set up the source and target pictures src = makePicture("horse.jpg") canvas = makeEmptyPicture(1000,1000) # Now, do the actual copying targetX = 0 width = getWidth(src) for sourceX in range(0,getWidth(src)): targetY = 0 for sourceY in range(0,getHeight(src)): color =

getColor(getPixel(src,sourceX,sourceY)) # Change is here setColor(getPixel(canvas,targetY,width -

targetX - 1), color) targetY = targetY + 1 targetX = targetX + 1 show(canvas) return canvas

ScalingScaling a picture (smaller or larger) has to do

with sampling the source picture differentlyWhen we just copy, we sample every pixelIf we want a smaller copy, we skip some pixels

We sample fewer pixelsIf we want a larger copy, we duplicate some

pixels We over-sample some pixels

Scaling the horse face downdef copyHorseFaceSmaller(): # Set up the source and target pictures src=makePicture("horse.jpg") canvas = makeEmptyPicture(82,155) # Now, do the actual copying sourceX = 104 for targetX in range(0,int(163/2)): sourceY = 114 for targetY in range(0,int(308/2)): color = getColor(getPixel(src,sourceX,sourceY)) setColor(getPixel(canvas,targetX,targetY), color) sourceY = sourceY + 2 sourceX = sourceX + 2 show(canvas) return canvas

Scaling the picture downdef copyBarbsFaceSmaller(): # Set up the source and target pictures barbf=getMediaPath("barbara.jpg") barb = makePicture(barbf) canvasf = getMediaPath("7inX95in.jpg") canvas = makePicture(canvasf) # Now, do the actual copying sourceX = 45 for targetX in range(100,100+((200-45)/2)): sourceY = 25 for targetY in range(100,100+((200-25)/2)): color = getColor(getPixel(barb,sourceX,sourceY)) setColor(getPixel(canvas,targetX,targetY), color) sourceY = sourceY + 2 sourceX = sourceX + 2 show(barb) show(canvas) return canvas

Scaling Up: Growing the pictureTo grow a picture, we

simply duplicate some pixels

We do this by incrementing by 0.5, but only use the integer part.

>>> print int(1)1>>> print int(1.5)1>>> print int(2)2>>> print int(2.5)2

Scaling up

def copyHorseLarger(): # Set up the source and target pictures src = makePicture("horse.jpg") w = getWidth(src) h = getHeight(src) canvas = makeEmptyPicture(w*2,h*2) srcPixels = getPixels(src) trgPixels = getPixels(canvas) trgIndex = 0 # Now, do the actual copying for pixel in srcPixels: color = getColor(pixel) # Once trgPixel = trgPixels[trgIndex] setColor(trgPixel,color) trgIndex = trgIndex + 1 # Twice trgPixel = trgPixels[trgIndex] setColor(trgPixel,color) trgIndex = trgIndex + 1 show(canvas) return canvas

Scaling up just the Facedef copyHorseFaceLarger(): # Set up the source and target pictures src=makePicture("horse.jpg") canvas = makeEmptyPicture(163*2,308*2) # Now, do the actual copying sourceX = 104 for targetX in range(0,163*2): sourceY = 114 for targetY in range(0,308*2): srcpx = getPixel(src,int(sourceX),int(sourceY)) color = getColor(srcpx) setColor(getPixel(canvas,targetX,targetY), color) sourceY = sourceY + 0.5 sourceX = sourceX + 0.5 show(canvas) return canvas

Scaling the picture updef copyBarbsFaceLarger(): # Set up the source and target pictures barbf=getMediaPath("barbara.jpg") barb = makePicture(barbf) canvasf = getMediaPath("7inX95in.jpg") canvas = makePicture(canvasf) # Now, do the actual copying sourceX = 45 for targetX in range(100,100+((200-45)*2)): sourceY = 25 for targetY in range(100,100+((200-25)*2)): color = getColor(getPixel(barb,int(sourceX),int(sourceY))) setColor(getPixel(canvas,targetX,targetY), color) sourceY = sourceY + 0.5 sourceX = sourceX + 0.5 show(barb) show(canvas) return canvas

Scaling up: How it worksSame basic setup as

copying and rotating:

Scaling up: How it works 2But as we increment

by only 0.5, and we use the int() function, we end up taking every pixel twice.

Here, the blank pixel at (0,0) in the source gets copied twice onto the canvas.

Scaling up: How it works 3Black pixels gets

copied once…

Scaling up: How it works 4And twice…

Scaling up: How it ends upWe end up in the

same place in the source, but twice as much in the target.

Notice the degradation: Gaps that weren't there

previously Curves would get “choppy”:

Pixelated

What to do?How do we clear up the degradation of

scaling up?Variety of techniques, but mostly following

the same basic idea:Use the pixels around to figure out what color

a new pixel should be, then somehow (e.g., by averaging) compute the right color.

Different techniques look at different pixels and compute different averages in different ways.

A simple Blurdef blur(source): target=duplicatePicture(source) for x in range(1, getWidth(source)-1): for y in range(1, getHeight(source)-1): top = getPixel(source,x,y-1) left = getPixel(source,x-1,y) bottom = getPixel(source,x,y+1) right = getPixel(source,x+1,y) center = getPixel(target,x,y) newRed=(getRed(top)+ getRed(left) + getRed(bottom) + getRed(right) + getRed(center))/5 newGreen=(getGreen(top) + getGreen(left) + getGreen(bottom)+getGreen(right)+getGreen(center))/5 newBlue=(getBlue(top) + getBlue(left) + getBlue(bottom) + getBlue(right)+ getBlue(center))/5 setColor(center, makeColor(newRed, newGreen, newBlue))

A different blurdef blur(pic,size): for pixel in getPixels(pic): currentX = getX(pixel) currentY = getY(pixel) r = 0 g = 0 b = 0 count = 0 for x in range(currentX - size,currentX + size): for y in range(currentY - size, currentY + size): if(x<0) or (y<0) or (x >= getWidth(pic)) or (y

>=getHeight(pic)): pass # Skip if we go off the edge else: r = r + getRed(getPixel(pic,x,y)) g = g + getGreen(getPixel(pic,x,y)) b = b + getBlue(getPixel(pic,x,y)) count = count + 1 newColor = makeColor(r/count,g/count,b/count) setColor(pixel,newColor)

We'll see pass and else later, but you can probably get a sense here of what's going on.

Blurring out the pixelation

Average from four sides, to compute new color

Things to try:Can you come up with general copy, rotate,

copy, and scale functions?Take input pictures and parametersReturn the canvas the correct transformation

appliedAlso think about generalizing the

transformations:Scaling up and down by non-integer amountsRotating by something other than 90 degree

increments

Blending picturesHow do we get part of one picture and part of

another to blur together, so that we see some of each?It's about making one a bit “transparent.”Video cards sometimes support this transparency

in hardware, called an alpha level to each pixel.We do it as a weighted sum

If it's 50-50, we take 50% of red of picture1's pixels + 50% of red of picture2's pixels, and so on for green and blue, across all overlapping pixels.

Example blended picture

Blended here

Blending code (1 of 3)def blendPictures(): barb = makePicture(getMediaPath("barbara.jpg")) katie = makePicture(getMediaPath("Katie-smaller.jpg")) canvas = makePicture(getMediaPath("640x480.jpg")) #Copy first 150 columns of Barb sourceX=0 for targetX in range(0,150): sourceY=0 for targetY in range(0,getHeight(barb)): color = getColor(getPixel(barb,sourceX,sourceY)) setColor(getPixel(canvas,targetX,targetY),color) sourceY = sourceY + 1 sourceX = sourceX + 1

Straightforward copy of 150 column's of Barb's picture

Blending code (2 of 3) #Now, grab the rest of Barb and part of Katie # at 50% Barb and 50% Katie overlap = getWidth(barb)-150 sourceX=0 for targetX in range(150,getWidth(barb)): sourceY=0 for targetY in range(0,getHeight(katie)): bPixel = getPixel(barb,sourceX+150,sourceY) kPixel = getPixel(katie,sourceX,sourceY) newRed= 0.50*getRed(bPixel)

+0.50*getRed(kPixel) newGreen=0.50*getGreen(bPixel)

+0.50*getGreen(kPixel) newBlue = 0.50*getBlue(bPixel)

+0.50*getBlue(kPixel) color = makeColor(newRed,newGreen,newBlue) setColor(getPixel(canvas,targetX,targetY),color) sourceY = sourceY + 1 sourceX = sourceX + 1

Here's the trick. For each pixel, grab 50% of each red, green and blue

Blending code (3 of 3) # Last columns of Katie sourceX=overlap for targetX in

range(150+overlap,150+getWidth(katie)): sourceY=0 for targetY in range(0,getHeight(katie)): color = getColor(getPixel(katie,sourceX,sourceY)) setColor(getPixel(canvas,targetX,targetY),color) sourceY = sourceY + 1 sourceX = sourceX + 1 show(canvas) return canvas

Drawing lines on Carolina

def lineExample():

img = makePicture(pickAFile())

verticalLines(img)

horizontalLines(img)

show(img)

return img

 

def horizontalLines(src):

for x in range(0,getHeight(src),5):

for y in range(0,getWidth(src)):

setColor(getPixel(src,y,x),black)

 

def verticalLines(src):

for x in range(0,getWidth(src),5):

for y in range(0,getHeight(src)):

setColor(getPixel(src,x,y),black)

We can use the color name “black” – it's pre-defined for us.

Yes, some colors are already definedColors defined for you already: black, white,

blue, red, green, gray, lightGray, darkGray, yellow, orange, pink, magenta, and cyan

That's tediousThat's slow and tedious to set every pixel you

want to make lines and text, etc.What you really want to do is to think in

terms of your desired effect (think about “requirements” and “design”)

New functionsaddText(pict,x,y,string) puts the string

starting at position (x,y) in the pictureaddLine(picture,x1,y1,x2,y2) draws a line

from position (x1,y1) to (x2,y2)addRect(pict,x1,y1,w,h) draws a black

rectangle (unfilled) with the upper left hand corner of (x1,y1) and a width of w and height of h

addRectFilled(pict,x1,y1,w,h,color) draws a rectangle filled with the color of your choice with the upper left hand corner of (x1,y1) and a width of w and height of h

The mysterious red box on the beachdef addABox(): beach = makePicture(getMediaPath("beach-

smaller.jpg")) addRectFilled(beach,150,150,50,50,red) show(beach) return beach

Example picturedef littlepicture(): canvas=makePicture(getMediaPath("640x480.jpg")) addText(canvas,10,50,"This is not a picture") addLine(canvas,10,20,300,50) addRectFilled(canvas,0,200,300,500,yellow) addRect(canvas,10,210,290,490) return canvas

A thought experimentLook at that previous page: Which has a

fewer number of bytes?The program that drew the pictureThe pixels in the picture itself.

It's a no-brainerThe program is less than 100 characters (100

bytes)The picture is stored on disk at about 15,000

bytes

Vector-based vs. Bitmap Graphical representationsVector-based graphical representations are

basically executable programs that generate the picture on demand.Postscript, Flash, and AutoCAD use vector-

based representationsBitmap graphical representations (like JPEG,

BMP, GIF) store individual pixels or representations of those pixels.JPEG and GIF are actually compressed

representations

Vector-based representations can be smallerVector-based representations can be much

smaller than bit-mapped representationsSmaller means faster transmission (Flash and

Postscript)If you want all the detail of a complex picture,

no, it's not.

But vector-based has more value than that

Imagine that you're editing a picture with lines on it. If you edit a bitmap image and extend a line, it's just more bits.

There's no way to really realize that you've extended or shrunk the line.

If you edit a vector-based image, it's possible to just change the specification Change the numbers saying where the line is Then it really is the same line

That's important when the picture drives the creation of the product, like in automatic cutting machines

How are images compressed?Sometimes lossless using techniques like run

length encoding (RLE)Instead of this:

B B Y Y Y Y Y Y Y Y Y B BWe could say “9 Y's” like this:

B B 9 Y B BLossy compression (like JPEG and GIF) loses detail, some

of which is invisible to the eye.

When changing the picture means changing a program…In a vector-based drawing package, changing

the drawing is changing a program.How could we reach in and change the actual

program?We can using string manipulation

The program is just a string of charactersWe want to manipulate those characters, in

order to manipulate the program

Example programmed graphicIf I did this right, we

perceive the left half as lighter than the right half

In reality, the end quarters are actually the same colors.

Building a programmed graphicdef greyEffect(): file = getMediaPath("640x480.jpg") pic = makePicture(file) # First, 100 columns of 100-grey grey = makeColor(100,100,100) for x in range(1,100): for y in range(1,100): setColor(getPixel(pic,x,y),grey) # Second, 100 columns of increasing greyness greyLevel = 100 for x in range(100,200): grey = makeColor(greyLevel, greyLevel, greyLevel) for y in range(1,100): setColor(getPixel(pic,x,y),grey) greyLevel = greyLevel + 1

# Third, 100 colums of increasing greyness, from 0 greyLevel = 0 for x in range(200,300): grey = makeColor(greyLevel, greyLevel, greyLevel) for y in range(1,100): setColor(getPixel(pic,x,y),grey) greyLevel = greyLevel + 1 # Finally, 100 columns of 100-grey grey = makeColor(100,100,100) for x in range(300,400): for y in range(1,100): setColor(getPixel(pic,x,y),grey) return pic

Another Programmed Graphicdef coolpic():

canvas=makePicture(getMediaPath("640x480.jpg"))

for index in range(25,1,-1): color = makeColor(index*10,index*5,index)

addRectFilled(canvas,0,0,index*10,index*10,color) show(canvas) return canvas

And anotherdef coolpic2(): canvas=makePicture(getMediaPath("640x480.jpg")) for index in range(25,1,-1): addRect(canvas,index,index,index*3,index*4)

addRect(canvas,100+index*4,100+index*3,index*8,index*10)

show(canvas) return canvas

Why do we write programs?Could we do this in Photoshop? Maybe

I'm sure that you can, but you need to know how.

Could I teach you to do this in Photoshop? MaybeMight take a lot of demonstration

But this program is an exact definition of the process of generating this pictureIt works for anyone who can run the program,

without knowing Photoshop

We write programs to encapsulate and communicate processIf you can do it by hand, do it.If you need to teach someone else to do it,

consider a program.If you need to explain to lots of people how to

do it, definitely use a program.If you want lots of people to do it without

having to teach them something first, definitely use a program.