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Computers in Radiology |
1 Department of Regional Radiology, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH 44195.
Received October 22, 2003; accepted after revision December 18, 2003.
Address correspondence to O. Lababede
(lababeo{at}ccf.org).
OBJECTIVE. This article, the second of two parts, suggests some practical applications for image manipulation using the 2002 version of PowerPoint.
CONCLUSION. Applications include enhancing previously manipulated images and manipulating unedited images. The user can develop his or her preferred techniques of image editing.
The previous article (part 1) [1] reviewed the image-manipulation commands of PowerPoint (2002, Microsoft), their limitations, and their advantages. By becoming familiar with these commands, the user can develop his or her preferred techniques in image manipulation. These techniques will naturally be perfected over time, through trial and error. This article explains my approach and presents my suggestions for using some of the practical applications of Power-Point image manipulation. The discussion is divided in two main categories: first, enhancing previously manipulated images in a presentation and second, manipulating unedited images for use in a presentation.
Enhancing Edited Images in a Presentation
Images in digital presentations may be obtained from a personal digital archive and from other sources, including imported digital images from PACS and hard-copy images. Hard-copy images such as films and slides need to be converted to digital form by scanners or digital cameras. Usually raw digital images require editing with image-manipulation programs before they can be incorporated into slides [2–4]. Unfortunately, it is difficult to set standards for the image-editing outcomes because whether digital images are assembled from a personal collection or newly acquired, variations in appearance are inevitable. Variations may stem from the degree of cropping, brightness, contrast, or color mode. Even with the application of macros, which automate a series of actions in some image-manipulation programs, differences may still be apparent in the final images.
The user can take several steps to eliminate or minimize undesirable variations. The first step is to display the presentation in thumbnail form using Slide Sorter view. This view can be selected from the main toolbar by clicking View, and selecting Slide Sorter (Fig. 1). Slide Sorter view displays the overall appearance of a presentation. Although minor variations among single-image slides can be tolerated, major differences in image appearance should be eliminated by adjusting the suboptimal images individually. To change an image in a particular slide, select the slide from Slide Sorter by double-clicking it. Then select the image by clicking it, and apply one or more of the following commands:
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Crop can be used to adjust differences in the field of view. If a significant portion of an image is cropped, the file size can be reduced through permanent deletion of the cropped areas, using the Compress Pictures command.
More Contrast or Less Contrast and More Brightness or Less Brightness commands adjust differences in contrast and brightness, respectively. These commands should be implemented only if they would not adversely affect the clarity of radiologic findings.
Format Picture enables the user to apply fine adjustments in brightness, contrast, and cropping. It can also be used to reverse one or more changes made to an image. Note, however, that cropped areas that have been deleted cannot be restored.
Compress Pictures can be used to reduce the image file size on a slide, such as a slide containing images prepared for printed publication at a resolution of 300 dots per inch (dpi). Compression obviates saving an additional copy of the image at lower resolution.
Slides with multiple images can be adjusted in similar fashion (Figs. 2A and 2B). Adjustments affect only the selected images. To adjust multiple images simultaneously, select the images before using the editing commands. To select more than one image, click on the first one, and then hold down the Shift button while clicking the other images.
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In addition to enhancing the overall appearance of a presentation, image-editing commands can be used to emphasize certain elements of an image and to manage space. A specific finding on a stored image can be shown by cropping the original without creating a new image (Figs. 3A and 3B). Adding text or arrows can also emphasize a finding. The quality of added text and arrows in PowerPoint is better than the quality of those added in image-manipulation programs, especially in relatively small images. Cropping enables the user to manage space efficiently by showing only a portion of an image (Figs. 4A and 4B).
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Manipulating Unedited Images to Be Used in a Presentation
The preferred method for editing imported images before incorporating them into slides is to use image-manipulation programs. However, PowerPoint image-editing commands can substitute for image-manipulation programs under certain circumstances. PowerPoint commands can be used when other dedicated software is unavailable (for example, in temporary workplaces). Moreover, PowerPoint tools are often adequate when the original images require minimal editing or when the time available for preparing a presentation is limited. Finally, PowerPoint commands can be helpful for users who are unfamiliar with more complex professional programs.
The order of the editing steps described here is not absolute. However, the editing process is considerably facilitated if certain steps are performed in a particular order.
After importing a digital image into the PC, the image should be inserted into the slide. One can use the main menu or the Insert Picture command from the Drawing toolbar. This technique has been described in part 1 of this article and in the literature [5, 6]. Sometimes, especially with large images, an image may appear larger than the slide area and only a portion of the image may be visible. Select the image by clicking on it before applying any of the editing commands. The presence of sizing handles (small circles at the corners and sides of image) indicate that the image is currently selected. If the image is too large, use the horizontal and vertical scroll bars until you see a corner of the image. Drag the corner handle toward the center of the slide until the image approximately fits in the slide area (Figs. 5A and 5B). If the image is not centered correctly, click in the middle of the image and drag it inside the slide margins.
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Step 1: Orientation
An image sometimes requires rotation or flipping. Use the Rotate Left
command from the Picture toolbar to rotate the image 90° to the left. This
command can be repeated for 180° or 270° rotations. Other types of
rotation and orientation such as Rotate Right, Flip Horizontal, and Flip
Vertical are available on the Drawing toolbar. Slightly tilted (crooked)
images that require less than 90° rotation will be corrected later in the
editing process (in step 6).
Step 2: Cropping
The Crop tool is needed to remove unwanted margins from an image
(Fig. 6). Removing such
margins makes it possible to emphasize the more useful portions of an image,
and it also reduces the size of the slide file. Unlike cropping with
image-manipulation programs, PowerPoint cropping does not by itself reduce the
image size; it hides unwanted edges, which remain available and can be
revealed by dragging the handles in the opposite direction. However, cropping
is essential for reducing the image size when using the Compress Pictures
command. Extra margins should be kept in tilted (crooked) images for later
use.
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Step 3: Adjusting the Dimensions and Position of an Image Relative to the Slide Area
The image size can be adjusted by dragging one of the corner handles toward
or away from the center. To avoid distortion and to maintain width-to-height
proportions, do not use the side handles. Tilted (crooked) images should not
be stretched to the maximum available dimensions at this point. Image
positioning in the slide can be adjusted with the Align or Distribute option
from the Drawing toolbar. Select Relative to Slide, and then open the menu
(Draw 
Align or Distribute). Select one or more of the options (Align
Left, Align Center, Align Middle, and so on)
(Fig. 7).
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Step 4: Adjusting Contrast and Brightness
More Contrast, Less Contrast, More Brightness, and Less Brightness commands
from the Picture toolbar can be used to enhance visualization of the image
findings. Use the Format Picture command to achieve fine adjustments in image
size, position, line style, brightness, contrast, and cropping.
Step 5: Conversion of Color Mode to Gray Scale
Images imported from some sources (e.g., scanners and digital cameras) are
saved in color. The Color command changes the color mode to gray scale, which
is an advantage because tints of blue and green are removed. As a result, the
uniformity of a presentation is enhanced. (Images with color information such
as color Doppler sonograms should not be converted.) Unlike converting to gray
scale with image-manipulation programs, changing the color mode to gray scale
in PowerPoint does not reduce the file size.
Step 6: Correcting Tilted (Crooked) Images
Images can be rotated simply by dragging the green circle, located above
the upper side handle, to a desired direction and degree
(Fig. 8). Alternatively, Free
Rotate, from the Drawing toolbar, can be used. When this option is selected,
the corner handles turn green. Drag one of these handles to the appropriate
direction and degree, and then click outside the image to save the result.
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One of the limitations of PowerPoint image editing is that the cropping margins parallel the rotated margins of the image, not the margins of the slide. This is problematic for images rotated to an angle other than 90°, 180°, or 270°. To compensate for this limitation, one can rotate the image, and then cover the angled margins with rectangular AutoShapes (Fig. 9). The color of these rectangles should match the background as closely as possible. (With patterned backgrounds, this technique has limited usefulness.) The color of the rectangle and its margin can be changed from the default settings by right-clicking on the rectangle and selecting Format AutoShape from the menu. On the Format AutoShape dialog box, select the Color and Lines tab, and change the Fill and Line colors. To avoid repeating the process for each of the four rectangles successively, select all of them by holding down the Shift key while left-clicking each rectangle. Then proceed as just described.
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Step 7: Image Compression
The Compress Pictures command can be used to reduce image size by changing
resolution to 96 or 200 dpi or by discarding the hidden cropped portions of
the image. Changing the resolution is a crucial step because the benefits of
reducing size always come at the expense of quality. Compression should be
balanced to preserve acceptable quality while achieving a smaller file size.
The best approach is to start using a reasonable setting and format for the
original image production. For example, set the digital camera or scanner
output close to 1024 x 768 at 96 dpi with JPEG format.
To illustrate the efficiency of compression, I used an unusual example in the accompanying figures. The original image for Figures 5A and 5B was scanned at 300 dpi and was saved as 5048 x 4140 pixels in TIFF format. The size was approximately 20 MB. The file size of one slide containing this image (such as the slide in Figs. 5A and 5B) was 11.6 MB, which is 60% of the original image size. The same slide file size can be reduced to 8.5 MB by applying the Delete Cropped Areas of the Picture option from the Compress Pictures dialog box. Applying both the Delete Cropped Areas of Picture and Compress Pictures options and changing the resolution to 96 dpi reduces the slide file size to only 505 KB, which represents an approximately 23-fold decrease from the slide file size of 11.6 MB to 4% of the original size.
Step 8: Removing Unwanted Data
Removing unwanted data, such as patient information, stray markings, or
scratches can be performed by adding AutoShapes from the Drawing toolbar.
However, this method is of limited value and should be avoided for editing
scratches or marks that overlay a physical structure (e.g., a body organ). If
an AutoShape is absolutely needed, it should be recognizable, to avoid
mimicking an abnormal entity. To customize the lines and color of a geometric
shape, right-click on the shape and select Format AutoShape.
Step 9: Labeling an Image and Adding Arrows or Text
To add an arrow, use the Arrow command from the Draw toolbar. To add a
caption or text to an image, use Text Box from the Drawing toolbar
(Fig. 10). These techniques
were discussed in detail in Part 1
[1]. Note that the Reset
Pictures command can be used to reverse all changes that were made to an image
and restore its original state. On the other hand, the Format Picture button
on the Picture toolbar restores only selected changes. Finally, remember that
some options from the Compress Pictures dialog box are irreversible.
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Conclusion
The 2002 version of PowerPoint has many useful image-manipulation features. This article, the second of two parts, has suggested some practical applications of PowerPoint image manipulation. These applications included enhancing previously manipulated images and manipulating unedited images. The user can develop his or her preferred techniques of image editing. Such techniques and skills will improve with practice over time.
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