• Sit with project partners!

Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • A Few Project Techniques.
  • Questions.
• Quiz.
• Project work time.

Preliminaries

Admin

• Review sessions next week
  • Zachary (Monday)
• Friday PSA.
  • If you choose to partake, please do so responsibly.
  • Remember that consent is necessary.

Upcoming Work

• Projects: Next Tuesday at 10:30 p.m.
• Reading for Monday Analyzing Projedures
• No Lab Writeup.
• Exam 4 to be assigned Tuesday (due Monday of week 14).

Extra Credit Opportunities

• If possible, send me these in advance.

Academic

• Any visit to the current show in the Faulconer gallery.
• Learning Deconstructed Workshop Series, Tuesdays at 11 in JRC 209.
• Metropolitan Opera Simulcast, November 21, 11:30 a.m. Lulu by Berg, Harris Cinema. (Warning! It's about four hours long.)
• Saturday Night's Silent Film + Live Score.
• Talk on the Future of Libraries, Monday, noon.

Peer Support

• Translations (a play). 7:30 p.m. Thursday through Saturday, 2:00 p.m. Sunday. Tickets at the Box Office.
• Smash Brothers Tournament, Saturday. (See signs around campus for more details.)
  • Novice players encouraged.

Miscellaneous

• 20+ minutes of fun in the snow.

Regular Peer Support

• Pals of PALS, pals@grinnell.edu, normally Saturday at 7:45 am (breakfast included; felines only), and Mondays at 4:45. Requires sign up in advance. MORE HELP NEEDED!
• Socrates Cafe', Saturdays, Younker, 2pm.
• Pun Club, Saturdays, 4pm, Way over Younker.

Upcoming Peer Support

• Women's Basketball vs. Beloit, Nov. 28 at 3:00 p.m.
• Women's Basketball vs. St. Norbert, Dec. 5 at 3:00 p.m.
• One-act Festival Dec. 5 & 6.
• Women's Basketball vs. Carroll, Dec. 12 at 3:00 p.m.

Other Good Things (No Extra Credit)

• Diwali event Friday.
• Jingle Bell Holiday Friday.
  • Boy Scouts will be selling tenderloins in the Methodist church from about 5-7pm.
  • If you show up, I'll treat you to a tenderloin or chicken sandwich or potato.

Project Ideas and Questions

How do I copy and paste from one image to another?

;;; Procedure:
;;;   new-copy-paste!
;;; Parameters:
;;;   source, an image
;;;   source-left, a non-negative integer
;;;   source-top, a non-negative integer
;;;   source-width, a positive integer
;;;   source-height, a positive integer
;;;   target, an image
;;;   target-left, a non-negative integer
;;;   target-top, a non-negative integer
;;;   target-width, a positive integer
;;;   target-height, a positive integer
;;; Purpose:
;;;   Copy one rectangular region of the image to a rectangular
;;;   region in another image, resizing as necessary.
;;; Produces: 
;;;   [Nothing; called for the side effect]
;;; Preconditions:
;;;   0 <= source-left < (image-width source)
;;;   0 <= source-top < (image-height source)
;;;   (+ source-left source-width) < (image-width source)
;;;   (+ source-top source-height) < (image-height source)
;;;   0 <= target-left < (image-width target)
;;;   0 <= target-top < (image-height target)
;;;   (+ target-left target-width) < (image-width target)
;;;   (+ target-top target-height) < (image-height target)
;;; Postconditions:
;;;   The specified area of the target image now contains the same subimage
;;;   as the source area (scaled, as appropriate).
(define new-copy-paste!
  (lambda (source 
           source-left source-top source-width source-height
           target
           target-left target-top target-width target-height)
    (let ([source-layer (image-get-layer source)]
          [target-layer (image-get-layer target)])
      (image-select-rectangle! source REPLACE 
                               source-left source-top 
                               source-width source-height)
      (gimp-edit-copy source-layer)
      (image-select-rectangle! target REPLACE
                               target-left target-top
                               target-width target-height)
      (let ([pasted (car (gimp-edit-paste target-layer 1))])
        (image-select-nothing! source)
        (image-select-nothing! target)
        (gimp-layer-scale pasted target-width target-height 1)
        (gimp-image-flatten target)
        (context-update-displays!)))))

How can I select a non-rectangular region, such as a triangle?

(image-select-polygon! image REPLACE (cons x1 y1) (cons x2 y2) ... )

For example

    > (define kitten (image-show (image-load "/home/rebelsky/Desktop/kitten.jpg")))
    > (image-select-polygon! kitten REPLACE (cons 140 120) (cons 160 15) (cons 200 80))
    '()
    > (image-transform! kitten irgb-complement)

How can I get a semi-transparent overlay?

First, select a portion of the image.

Next, use (image-transform! image (lambda (col row) ...)).

Finally, select nothing.

Are there other things like image-transform!?

We also have image-recompute!, which is like image-compute!, but works on an existing image.

    > (image-recompute! kitten (lambda (col row)
                                 (modulo (* col row row col col) (irgb 255 255 255))))

Questions

Quiz

Project work time