1. Test 2 on Wed, 11/9 On image processing
Allowed to use JES to test your code, but discouraged
Last day to withdraw with W: 11/15

2. Pixels and Pictures Pixels are picture elements
Each pixel has colors from (0,0,0) to (255,255,255)
pixel = picture.getPixel(x,y)
color = makeColor(r,g,b)
pixel.setColor(color)
A picture is a matrix of pixels
Columns (x coordinate) from 0 to width-1
Rows (y coordinate) from 0 to height-1

3. Picture Functions ppp =makePicture(pickAFile())
ppp.getWidth(), ppp.getHeight()
xxx=ppp.getPixel( , )
xxx.getColor(), .getRed(), .getGreen(), .getBlue()
xxx.setColor(), .setRed(), .setGreen(), .setBlue()
makeColor(), pickAColor()

4. Image Processing Draw a line
Paint pixels to red
Picture negative (Paint pixels to complements)
Get r,g,b of a pixel, repaint it with (255-r, 255-g, 255-b)
Picture gray scale
Get r,g,b of a pixel, bw = int((r+g+b)/3), repaint it with (bw,bw,bw)
Sunset, posterize
Pixels are organized in a grid

5. Gray Scale picture def pixBW(pixel): # given a pixel, change to BW
get R,G,B values of the pixel
compute the average
set R,G,B values of the pixel to the average
return
def picBW(pic):
get the width of pic, and name it
get the height of pic, and name it
for every y coordinate:
for every pixel in the row at the given row y:
call pixBW(pixxx)

6. Gray Scale picture def pixBW(pixel): # given a pixel, change to BW
r=pixel.getRed() # get R,G,B values of the pixel
g = pixel.getGreen()
b = pixel.getBlue()
avg = int((r+g+b)/3) # compute the average
bw= makeColor(avg, avg, avg)
pixel.setColor(bw) # set R,G,B values to the average
return
def picBW(pic):
wid = pic.getWidth() # get the width of pic, and name it
hgt = pic.getHeight() #get the height of pic, and name it
for y in range(hgt): # for every y coordinate:
for x in range(wid): # for every pixel in the row
pixBW(pic.getPixel(x,y)) # call pixBW(pixxx)

7. Additional Picture Functions
setMediaPath() – fix a path to media files
getMediaPath(filename)
file = makeEmptyPicture(100,100) – creates a blank picture of size 100x100
writePictureTo(file, getMediaPath()+“\newpic.jpg”) – save file with name “100x100.jpg”
canvas=makePicture(getMediaPath(“newpic.jpg”))

8. Picture Copy copy.py with Two pictures
‘pictA’ to copy to ‘pictB’ (pictB has to larger than pictA)
def picCopy(fromPic, toPic):
# for every pixel in fromPic, copy its colors to the same pixel location in the toPic
def main():
setMediaPath()
picA = makePicture(getMediaPath(“ “)
# get the width of picA
# get the height of picA
# create an empty picture, called picB, with the same dimension
picCopy(picA, picB)
repaint(pictB)

9. Picture Copy copy.py with Two pictures
‘pictA’ to copy to ‘pictB’ (pictB has to larger than pictA)
def picCopy(fromPic, toPic):
hgt = fromPic.getHeight()
wid = fromPic.getWidth()
for y in range(hgt):
for x in range(wid):
pixF = fromPic.getPixel(x,y)
col = pixF.getColor()
pixT = toPic.getPixel(x,y)
pixT.setColor(col)
return
def main():
setMediaPath()
picA = makePicture(getMediaPath(“ “)
hgt = fromPic.getHeight()
wid = fromPic.getWidth()
# create a picture in same dimension
picB = makeEmptyPicture(wid, hgt)
picCopy(picA, picB)
repaint(pictB)

10. Copy flower1 to lower left corner
sourceX
sourceY
flower1
targetX = sourceX
targetY = sourceY + ?
? : getHeight(canvas) – getHeight(flower1)

11. Copy flower2 targetX = sourceX + getWidth(flower1)
sourceY
flower2
flower1
targetX = sourceX + getWidth(flower1)
targetY = sourceY + ?
? : getHeight(canvas) – getHeight(flower2)

12. Lab_1104 Modify picCopy() so that it has four arguments:
picCopy(fromPic, toPic, toX, toY)
where toX and toY are coordinates in toPic
from where pixels in fromPic have to be copied over
Create a large empty picture, called ‘canvas’
Copy flower1.jpg to canvas, and flower2.jpg to canvas next to flower1.jpg
updated copy.py to

13. Edge detection Pixel is different from its neighbors => an edge
Measure (criterion) of pixel differences ?
One possibility – compare B/W value of a pixel with those at the left and below
If differences are above threshold, then an edge (black), otherwise (white)
For each pixel in picture1:
get B/W values of the pixel, its left and below (how?)
if differences of (pixel, left) and (pixel, below) > Threshold
paint the pixel black
otherwise,
paint the pixel white