Creating an old time photo

1
Creating an old time photo

• I like the look of old black and white photos.
  Suppose that I want to turn an existing picture
  into an old time photo.
• What would I do?
• Remove the color from a picture?
• Turn every Pixel to either black or white?
• But there are more than two colors, there are
  also grays.

2
The concept of grayscale

• Gray is any color where the red, green, and blue
  values are all the same.
• Black is gray because all three values are set
  to 0.
• White is gray because all three values are set
  to 255.
• Dark-gray might be the color where all three
  values are set to 85 (roughly 1/3 from black to
  white).
• Light-gray might be the color where all three
  values are set to 170 (roughly 1/3 from white to
  black).
• How many different grays are there in our system?

3
So how do I decide what gray goes with what color?

• One solution is to find the average intensity
  of a pixel, and set the r, g, and b values to
  that intensity
• (red green blue) / 3

4
One version

• def makeGrayscale(picture)
• for pixel in getPixels(picture)
• redPart getRed(pixel)
• greenPart getGreen(pixel)
• bluePart getBlue(pixel)
• val (redPart greenPart bluePart)/3
• setRed(pixel,val)
• setGreen(pixel,val)
• setBlue(pixel,val)

5
The same results with different code

• def makeGrayscale(picture)
• for pixel in getPixels(picture)
• redPart getRed(pixel)
• greenPart getGreen(pixel)
• bluePart getBlue(pixel)
• val (redPart greenPart bluePart)/3
• setColor(pixel,makeColor(val,val,val))

6
What about different results with different code

• Introducing PA01
• Three tasks
• Create a flexible modifyRed() method
• Create several versions of makeGrayscale()
• Create a makeSepiaTone() method
• One report
• Submitted by placing on your p drive by next
  Friday

7
What would I need to do

8
to make this?
9
What is different?

• Why is this problem different from the kinds of
  activities we looked at this week?
• It only works with some of the pixels.
• We have to have the ability to look at pixels
  based on position

10
What does this do?

• def mysteryMethod(picture)
• for x in range(1,getWidth(picture))
• for y in range(1,getHeight(picture))
• pixel getPixel(x,y)
• redPart getRed(pixel)
• greenPart getGreen(pixel)
• bluePart getBlue(pixel)
• val (redPart greenPart bluePart)/3
• setColor(pixel,makeColor(val,val,val))