Name: Email Username: Lab Date and Time: CSC 101: Lab #6 Digital Images Due Date: 5:00pm, day after lab session Lab Report: Answer the report questions in this document as you encounter them. Submit your answers to these questions by the deadline, as well as the three images you are asked to create. At the end of this document, you will be provided instructions on how to upload the images to be graded. Purpose: The purpose of this lab is to provide you with hands-on experience in digital image manipulation techniques using the Adobe Photoshop tool. The techniques should reinforce some of the ideas previously seen in lecture, introduce you to a few new topics you will cover in class this week, and add to your portfolio of digital experience (photo manipulation using Photoshop). Indexed color: Start Photoshop, and load from your lab6 folder the file tulips.psd. (If asked, tell Photoshop to Discard the Embedded Profile ). Note (visually) that this image of tulips contains only six colors. Choose the menu option Image Mode Indexed Color. Choose Exact for the Palette option, and None for the Forced option. Uncheck Transparency if it is checked, then click OK. Using these options, we will be able to see precisely which six colors the image is composed of. Now, we ve got to find where it presents the color information. Under the Window menu, scroll down and select the Info option if it is not already checked. This should open a new box in the interface, with three tabs at the top. Make sure the Info tab is chosen in this box (see figure at right). Now, move the mouse cursor over each of the six colors in the tulips image. As you move the mouse over the different colors, you will notice that the R(ed), G(reen) and B(lue) values will change in the Info Window, as will the Index number. Record the Index number of each color as you mouse over it (it will be labeled as Idx: in the INFO box under the R,G,B values) as your answer to Question 1. Question 1 (6 pts): Write in the color index values: Now, look at the indexed color table by selecting Image Mode Color Table. The color ordering should match what you wrote down!
Question 2 (4 pts): Find the green color in the color table (index 1) and click on it. Choose a new nongreen color in the color picker that appears. Which parts, if any, of the image of the tulips changed? Question 3 (3 pts): Now change the Table dropdown from Custom to System (Windows). The colors in the image have changed. Have the index numbers of the colors in the image changed? A. Yes B. No Question 4 (6 pts): Argue for or against the truth of this statement (based on what you have seen above): Indexed color images are very similar to paint-by-number, in that each pixel is tied to a number, and every instance of that number is painted the same color. Close the file tulips.psd you have been working on there is no need to save any changes you have made. Changing an object color within an image: Photoshop includes a number of powerful image editing tools. In this exercise, you will experiment with selecting part of the image and using the Replace Color tool (available on the Image Adjustments menu). You will need to work out the solution to this task on your own. If you cannot determine how to accomplish the task, please ask for assistance. Open the file thread.psd in Photoshop. Change the color of the front thread roll from orange to yellow, as shown in the figure below. For full credit, ensure that your change affects the orange roll in front and the orange reflection on the yellow-green roll at the top, but does not affect the more distant orange items in the lower right of the image. Figure 1. thread.psd before modification Figure 2. Same picture modified
When you have finished, use Save As to save the file in JPEG [Maximum Quality option] format, not in PSD format, with the name thread-mod.jpg (note this is a new filename). Question 5 (11 points): Describe how you solved this task. What Photoshop tools did you use? What settings, if any, were required on those tools? What steps did you have to perform? Are you satisfied with the results you achieved? Selectively replacing image content: In the previous exercise, you used Photoshop s tools to selectively change part of an image. In this exercise, you will use Photoshop to combine two images into a new, merged image. Open the file devils-tower.jpg in Photoshop. Also open the file sky.psd in Photoshop. Select the entire sky image in sky.psd (think of a good way to select all of an image) and then choose Edit Copy. Return to the Devils Tower image and experiment with Photoshop s Select Color Range command to find the best settings to select all of the sky and only the sky. In the Devil s Tower image, choose Edit Paste Into. The sky from the first image should have replaced the blue sky in the Devil s Tower image. Use the Move Tool to move the pasted sky image to an attractive location, making sure that all of the blue sky has been replaced. Compare your result to the sample image to the right. For full credit, your image should show no traces of the original blue sky, while retaining intact all of the trees and the rock tower. Use Save As to save the file in JPEG format [Maximum Quality option] with the name devils-tower-mod.jpg. Note that this idea is very much like using green screens in movie-making!
This is a good point to stop and make sure you are on the right track. If you are having trouble with anything, talk to one of the instructors. Cleaning up images: In this exercise, you will use Photoshop s Healing Brush and Patch Tool to remove distracting elements from an image. You have been provided with the file dam.jpg, a picture with elements obscuring parts of the image. Experiment with the Healing Brush and Patch Tool (look for the band-aid style tool - it s the 7 th in my list of tools; right-click on that icon to change between the Healing Brush and Patch Tool) to remove the distracting elements of the image. You should remove at least the four cables/power lines that cross the image AND the line of barrels that crosses the river downstream of the dam. Try to make your changes as neat and clean as possible so that your image modifications are not glaringly obvious and your updated image looks convincing. After you have completed your image updates, save the cleanedup image in your lab6 folder under the name after.jpg (in JPEG format, Maximum Quality option). Submission: Submit your answers to these questions by the deadline of 5:00pm the day after your lab session. In today s lab, you created three modified JPEG files: thread-mod.jpg devils-tower-mod.jpg after.jpg Upload the three images to Sakai using the Assignments, Lab 6 link by the lab submission deadline. A grade-sheet specifying how the 80 points for this lab document are distributed is included on the next page. The remaining 20 points for this lab come from the pre-lab.
CSC 101 Fall 2011 Lab #6 Gradesheet Topic Points Notes Pre-lab questions 20 total (10 @ 2 pts Recorded on pre-lab. each) Lab-report questions 30 total Submitted Image Grading Thread-mod.jpg: Front range spool changed completely to yellow. Thread-mod.jpg: Green spool shows yellow (not orange) reflection. Thread-mod.jpg: Distant spools (lower right of image) have not been turned to yellow. Thread-mod.jpg: Overall natural, convincing appearance. Devils-tower-mod.jpg: All Sky changed from blue to red/brown-cloud image Devils-tower-mod.jpg: New sky image does not overlap or obscure trees, ground, or Devil s tower. Devils-tower-mod.jpg: Overall natural, convincing appearance. After.jpg: Removal of downstream barrels After.jpg: Removal of all four cables After.jpg: Overall natural, convincing appearance. Total: of 80 for lab report