1 Introduction to Computer Graphics – CGS-1586C Spring Quarter 2011 Instructor: Amanda Dickinson Tues/Thurs from 6:00PM to 7:50 PM

2 Overview for Today  Wikispaces  Missed the quiz last Tuesday?  The Move Tool  The Slice Tool  Transforming Images  Putting Images Together  Histogram – Levels and Curves  Homework

3 Wikispaces  If you haven’t written down the wikispace link, here it is again.  Project details, weekly power points, and exercises that you need to complete will be on the wiki.  Now you can’t use the excuse “I missed that day’s work.” Haha!

4 Missed the quiz last Tuesday?  We had a pop quiz last Tuesday on a few important topics found in the powerpoints  The people that missed the quiz cannot take the quiz, it would be unfair  For the people that still want to get credit for that day, I have an alternative:

5 The Alternative  The alternative: Please write an essay IN YOUR OWN WORDS about one of these two topics:  Gestalt Theory OR  The Basics of Color Theory The essay must be  No less than 2 pages, double spaced  Your name must be on it, saved in usual last_firstname format  I will take points off for spelling errors, bad grammar, or if you get the facts wrong Closure, symmetry, sum is greater than the whole, etc The 2 color wheels, value, tone, primary colors, warm/cold colors etc Remember: This needs to be your own words, don’t just copy and paste from my powerpoints or from the internet. I’ll know.

6 When is the essay due?  The essay will be due Thursday, May 12 at the beginning of class.  Please print it.  Late papers will have grade reduced.

7 The Toolbox We went over some of the tools in blue, but not all of them…

8 The Move Tool  The move tool allows you to move a selection or entire layer by dragging it with your mouse or using your keyboard arrows keys. When the move tool is selected, click and drag anywhere in the image. By default, if an area is selected the selection will be moved, otherwise the whole layer will be moved. See the options bar for more options.  Alternatively, use your arrow keys to move the selection or layer in small increments. Hold down the Shift key to move in larger increments.  Note: You can activate the move tool when another tool is selected by holding down the Ctrl key (Windows) or Command key (Mac OS).

9 The Slice Tool  The Slice tool allows you to divide an image into smaller sections which fit together like a jigsaw (but with straight edges). The slice tool is located in the top section of the Photoshop Toolbox.  There are two tools: Slice (which creates the slices) and Slice Select (which enables you to select and modify existing slices).  Sliced images are commonly used for web design work, which sometimes requires images to be broken up in this way.

10 The Slice Tool

11 The Slice Tool  How to use Slice tool: Select the slice tool in the toolbox. Click and drag over the area you wish to make into a slice. Release the mouse button - Photoshop automatically creates the necessary number of slices, with the active slice highlighted. Using the slice select tool, you can move and resize slices by dragging inside a slice, or by dragging the handles.  Note: To export the separate images, choose File > Save for Web from the Photoshop menu. When you save the file you will have the option to save the images and/or a new HTML page to contain the images.

12 Transforming Images  Scaling Graphics One of the most basic transformations Photoshop is capable of is scaling a graphic. Scaling allows you to enlarge or shrink a graphic around a reference point. To scale a graphic, we go to Edit > Transform > Scale. A set of handles will appear around our selected elements in the document (such as layers, or shapes). By moving anyone of these handles, we can adjust the size of the object. To apply the transformation, hit Enter. The Transform Shortcut – CMD + T

13 Transforming Images

14 Transforming Images

15 Transforming Images  Rotating Graphics To Rotate an Object in Photoshop, go to Edit > Transform > Rotate. Handles will appear as they did with a Scaling Transform, but instead of dragging one of these, go just outside of the object until you see a curved arrow rotate icon. At this point, simple drag left or right to rotate the selected object. Once again, you must finish applying the transformation by pressing Enter.

16 Transforming Images

17 Transforming Images Be Precise with your Rotations! You can rotate in 15 Degree Increments by holding down shift while rotating.

18 Transforming Images  Skew, Distort, and Perspective Transformations The next 3 transformations are all similar, because they are all controlled by dragging handles. That is not to say that they are used to do the same thing, they simply all operate in the same manner. You can apply a Skew, Distort, or Perspective Transformation from Edit > Transform. Skew: Skew transformations slant objects either vertically or horizontally. Distort: Distort transformations allow you to stretch an image in ANY direction freely. Perspective: The Perspective transformation allows you to add perspective to an object.

19 Transforming Images

20 Transforming Images  Warping an Object The Warp Transformation is quite a bit different compared to the other transformations. The entire shape of the object can be modified, making this transformation useful for several different effects. To use a Warp Transformation go to Edit > Transform > Warp. A Mesh will appear over your object that you can adjust by dragging control points, lines, or any other area inside of it. You can additionally apply a preset warp from the options bar.

21 Transforming Images

22 Transforming Images Warped

23 Putting Images Together  Let’s say you want to combine two images into one file  One way to do it: Pull both images into Photoshop You will see tabs with the image names, pull these apart from each other into separate windows Use the move tool and drag one image into the other image The moved image will be put in a new layer with your other image

24 Putting Images Together  Another way is to use File > Place Image  There are probably other ways, but these are the most common

25 Histogram – Levels and Curves  Sometimes you take a photo and it’s too dark, too light, or a funny color  We can fix these problems using the Levels and Curves tools in Photoshop  Levels and curves use a type of histogram, but what IS a histogram?

26 Histogram – Levels and Curves  A histogram is a type of graph that shows the current tonal range of your image It shows how much of your image is pure black, pure white, and the bits in between (on both greyscale and color images) The Histogram Pallete 

27 Histogram – Levels and Curves  The best way to understand how the histogram actually works is to use it as a tool  The most common place to work with the histogram is when you adjust the levels of your image

28 Histogram – Levels and Curves  Open up levelpractice01.psd from the histogram folder. It’s in the course files on my computer, or on the wiki.  Save this file as lastname_firstname_levels01.psd Note how washed out the image is. We’re going to fix this using levels.

29 Histogram – Levels and Curves  Now, there are two ways of adjusting the levels or colors of an image Image > Adjustments > Levels  Permanently changing your photo Use Level Adjustment Layer  Uses a type of mask to preserve original photo

30 Histogram – Levels and Curves  We are going to use the adjustment layer for this project  Locate the adjustment layer button on the bottom of your layers pallete and click it

31 Histogram – Levels and Curves  A top down menu will appear Pick Levels from the drop down menu

32 Histogram – Levels and Curves  A new window will pop up revealing a histogram of the image This represents the range of dark and light pixels in your image Black is on the left, white is on the right It looks like a mountain range The gradient helps you remember which side is black and which side is white

33 Histogram – Levels and Curves  The output levels down below the graph tell us that the picture has 256 separate tonal values  Moving the triangles around will reduce the number of values causing the image to become bleached or darkened Note: We humans start counting at 1 while a computer starts at 0, that’s why it says 255 instead of 256.

34 Histogram – Levels and Curves  The “mountain range” is actually made up of 256 tiny little vertical columns, each representing a brightness value  The more pixels of a brightness value, the taller the column

35 Histogram – Levels and Curves  For example, a very dark picture has more columns on the left side of the histogram

36 Histogram – Levels and Curves  And a picture with a lot of bright white values has a lot of columns on the right of the histogram

37 Histogram – Levels and Curves  Anyways, let’s get back to adjusting our own picture  Note how our picture has no values on either side of the histogram, this is typical of a washed-out picture

38 Histogram – Levels and Curves  Drag the black triangle towards the edge of where our histogram starts to shoot upwards  Now drag the white triangle to where our brighter values begin to rise  Make sure preview is checked to see the results in real time! Your triangles should be about like this now

39 Histogram – Levels and Curves  This is the standard adjustment of a photo, but we are going to go further with this  We are going to move the grey triangle to the left to brighten up the midtone values of the image (to pop the details out)

40 Histogram – Levels and Curves  Now because we moved the grey triangle, we have lost some of the black colors  Move the black triangle a bit further to the right and move the white triangle a bit farther into the left of the histogram Your triangles should be around here now

41 Histogram – Levels and Curves  When you move your black or white point inside the curve your histogram like this, you are “clipping” your shadows or highlights and losing some detail in those areas. You are essentially telling Photoshop “treat every pixel darker than this as pure black” or as pure white on the highlight end.  Photoshop provides a neat trick to allow you to see exactly where your shadow or highlight clipping begins. Just hold down the ALT key (PC) or Option Key (Mac) as you drag the slider, and when you see color starting to appear, that indicates pixels where shadows or highlights are getting clipped.

42 Histogram – Levels and Curves Pressing alt or option key while sliding the triangles around will show you where your shadows/highlights are being clipped

43 Histogram – Levels and Curves  Save your file one final time  Note that if you click the eye in the adjustment layer it will toggle your new image look on or off  Put your file in your course folder before class is over today

44 Histogram – Levels and Curves  After enough practice with the level tool you will be able to tell if a picture needs adjustment or not  Now, onto curves!  These look a bit scary but they’re actually fun to mess with

45 Histogram – Levels and Curves  Please open up curvespractice01.psd  Save as lastname_firstname_curve01.psd

46 Histogram – Levels and Curves  Like before, make a new adjustment layer  Instead of clicking layers, click curves  The curves box will pop up

47 Histogram – Levels and Curves  Adjusting the curves of your picture is almost the same as adjusting the levels  The line found inside the grid can be adjusted and even curved (aka the name) to adjust the appearance of your image

48 Histogram – Levels and Curves  Let’s start like how we’d adjust the image using levels.  Grab the point on the bottom move it left towards where the black values begin  Grab the point on the top, move it to the right to where the white values begin

49 Histogram – Levels and Curves Be sure to keep the points on the top/bottom of the grid when adjusting them Note how your Histogram Pallete changes

50 Histogram – Levels and Curves  Notice that as soon as you click on the point, both the Input and Output readings below the bottom gradient bar show a value of 0, letting us know that the black point is currently set to a brightness value of 0 and we haven't yet made any changes.  As you drag the point horizontally towards the right, the Input reading increases while the Output reading remains at 0.  This tells us that whichever original brightness level we select with the point (the Input level) is being pulled down to level 0, or pure black (the Output level).

51 Histogram – Levels and Curves  As soon as you click on the point in the top right corner, you'll see the Input and Output readings display a value of 255, indicating that our white point is currently set to its maximum brightness value of 255 and we haven't yet made any adjustments.  As you drag the point towards the left, the Input reading changes while the Output reading remains at 255, telling us that whichever brightness level we select with the point is being pushed up to pure white.

52 Histogram – Levels and Curves  Now with curves, we can do a bit more with this picture  As you probably noticed, there is no midtone slider on the curve graph  With curves we can add points on the line for our midtone values, and we can add as many as we want!  To add a point, simply click the center of your curves line.

53 Histogram – Levels and Curves

54 Histogram – Levels and Curves  Let’s darken our midtones on this picture.  Drag your new point straight down, to about output 110, input 128  Note how your picture darkens

55 Histogram – Levels and Curves  The difference between levels and curves is that we can continue to add more points to adjust the image further  Let’s add another point on our line, click about halfway between the bottom point and the middle point.  Drag the point down a short distance to darken the shadows of our picture.

56 Histogram – Levels and Curves  Now to add some highlights  Add another point between the top point and middle point  Drag the point a bit upward

57 Histogram – Levels and Curves  Your curve should have a slight s-shape to it now  Take a look at your picture, toggle the adjustment layer eye to see the difference, pretty cool huh?  If you want to try out some more curve practice, check out the lesson in the book, page 132.  Save the file one more time and put it in your course folder on my computer.

58 Histogram – Levels and Curves  We’ll look at more tools that can adjust image colors on Thursday.  Please obtain at least two color stock image files for Thursday’s class.

59 Homework  Read Chapter 9 and 10 in Digital Foundations before next Tuesday.  Find at least 2 stock images to use for Thursday’s class exercise.  Finish any late assignments and turn them in asap.