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

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

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

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

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)

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)

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”))

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)

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)

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

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

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 Email updated copy.py to COMP1000.201@gmail.com

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