1. ITEC2110, Digital Media Chapter 3 Digital Image Processing 1 GGC -- ITEC2110 -- Digital Media

2.  Capturing Images  Digital Image Retouching  Color Adjustment  Selection Tools and Layer Basics  Output Images  Editing Vector Graphics Content 2

3.  the basic steps of image retouching  the tools for image retouching steps In this lecture, you will learn 3

4. 1.Crop and straighten the image 2.Repair small imperfections 3.Adjust the overall contrast or tonal range of the image 4.Remove color casts 5.Fine-tune specific parts of the image 6.Sharpen the image Basic Steps of Digital Image Retouching 4

5. Why?  The image may be tilted.  You may only want part of the image. Photoshop Tool:  Straighten tool (http://www.youtube.com/watch?v=jeURyi-60wE) (http://www.youtube.com/watch?v=jeURyi-60wE Step 1. Crop and Straighten 5

6. Why?  Scanned images: dirt and dust Photoshop Tools:  Clone Stamp (http://www.youtube.com/watch?v=WcJbN8CA49c) (http://www.youtube.com/watch?v=WcJbN8CA49c)  Healing Brush (http://www.youtube.com/watch?v=abav1P6nMVo) (http://www.youtube.com/watch?v=abav1P6nMVo) Step 2. Repair Small Imperfections 6

7. Why?  To maximize the tonal range of the image to improve contrast Photoshop Tools:  Image > Adjustment > Levels...  Image > Adjustment > Curves...  Image > Auto Tone  Image > Auto Contrast Step 3. Adjust overall contrast or tonal range of the image 7

8.  Adjust levels allows you to stretch the tonal range to improve image's brightness and contrast while maintaining the relative differences between colors.  Brightness/Contrast tool will alter the relative differences between colors.  Thus, in general, adjusting levels is preferred over the brightness/contrast tool. Adjust Levels vs. Brightness/Contrast 8

9. Histogram 9 An image with 4 colors Histogram of the image levels X-axis: the gray level (with the darkest value on the left) Y-axis: the relative number of pixels in the image that have the corresponding shade of gray

10. Adjust Levels Example 10 An image with 4 colors Histogram of the image levels

11. Adjust Levels Example 11 An image with 4 colors Stretching the histogram

12. Adjust Levels Example 12 After adjusting levels by stretching the histogram, the contrast of the image is increased. Histogram after stretching

13. Brightness/Contrast Example 13 After adjusting levels by stretching the histogram, the contrast of the image is increased. Histogram after using Brightness/Contrast tool Note the relative position of the color levels in the histogram

14. Why?  The image may contain color casts, i.e. appear tinted. Photoshop Tools:  Image > Adjustments > Color Balance...  Image > Adjustments > Auto Color (http://vimeo.com/7011236) Step 4. Removing Color Casts 14

15. Color Balance Example 15 An image with a purple tintColor Balance dialog box

16. Color Balance Example 16 The image after removing the purple tintColor Balance settings to remove the purple tint from the original image To remove a color cast: Move the sliders away from the label of the color that is the color cast you want to remove.

17. Color Balance Example 17 The image after removing the purple tintColor Balance settings to remove the purple tint from the original image For example, the purple tint contains a red tint. Thus, the first slider is moved away from red to remove the red tint.

18. Color Balance Example 18 The image after removing the purple tintColor Balance settings to remove the purple tint from the original image You may also choose to apply the color correction to the highlights, midtones, or shadows of the image.

19. Color Balance Example 19 The image after removing the blue tint in the darker areas Color Balance settings to remove the purple tint from the original image For example, the shadow areas have more blue tint than the rest of the image. You can select Shadows and move the sliders away from Blue and Cyan to selectively remove the blue tint from the darker areas.

20. Why?  You may want to apply different effects on small parts of the image. Photoshop Tools:  Dodge tool (to lighten by brushing) (http://www.youtube.com/watch?v=8tkbVlHDc7A) (http://www.youtube.com/watch?v=8tkbVlHDc7A)  Burn tool (to darken by brushing) (http://www.youtube.com/watch?v=emc6_AhCVBk) (http://www.youtube.com/watch?v=emc6_AhCVBk)  Sponge tool (to saturate/desaturate by brushing) (https://www.youtube.com/watch?v=2AEbIUQhIyM) (https://www.youtube.com/watch?v=2AEbIUQhIyM) Step 5. Fine-tuning specific parts of the image 20

21. Why?  There may be small distractions, such as power lines, small airplanes in the sky, a zit on the face. Photoshop Tools:  Clone Stamp tool Step 5. Fine-tune specific parts of the image 21

22. Example Application of Dodge and Burn Tool 22 The image before fineturning with dodge and burn The image after fineturning with dodge and burn

23. Example Application of Dodge and Burn Tool 23 The image before fineturning with dodge and burn The image after fineturning with dodge and burn The overexposed area is darken a little by burning.

24. Example Application of Dodge and Burn Tool 24 The image before fineturning with dodge and burn The image after fineturning with dodge and burn The shadows are burnt and the lighter areas are dodged to exaggerate the light and dark, thereby making the drum appear less flat.

25. Example Application of Clone Stamp Tool 25 The image before fineturning with the clone stamp tool The image after fineturning the clone stamp tool The paint on the drum is restored using the clone stamp tool.

26. Why?  Scanned images usually look a little soft- focused.  Scaling an image also can make the image soft- focused.  Even if your image is a straight digital photograph from a digital camera, it is a good idea to experiment with sharpening to see if it improves the image’s overall clarity. Photoshop Tools:  Filter > Sharpen > Unsharpen Mask... (http://www.youtube.com/watch?v=HcdSncXCIso) (http://www.youtube.com/watch?v=HcdSncXCIso) Step 6. Sharpen the image 26

27. Don't Over-sharpen! 27

28.  Try to keep the order of the steps  Performing these steps out of order or jumping back and forth among steps may cause unwanted effects on the image Order of the Steps 28

29.  Why should the sharpening be one of the final steps in the process?  Why should cropping be the first step before you do anything to the image in the image editing program?  What happens if you do the dodging and burning before removing the color casts? Order of the Steps 29

30. Review Questions Note to instructor: Depending on your preference, you may want to go over the review questions at the end of this lecture as an instant review or at the beginning of next lecture to refresh students' memory of this lecture. 30

31. Given here are the general steps of image retouching of a scanned image. Order the steps by labeling 1 through 6. ___ Remove color casts ___ Adjust the overall contrast or tonal range of the image ___ Crop and straighten the image ___ Sharpen the image ___ Repair small imperfections ___ Fine-tune specific parts of the image using Review Question 31

32. If the image has a green cast, how would you color correct it using Color Balance? Review Question 32

33. Both of the following tools can be used to increase contrast. However, ___ tool will alter the relative differences between colors. A.Image > Adjustments > Levels... B.Brightness/Contrast Review Question 33