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Computers in Radiology |
1 Department of Regional Radiology, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH 44195.
Received October 21, 2003; accepted after revision January 30, 2004.
Address correspondence to O. Lababede
(lababeo{at}ccf.org).
OBJECTIVE. This article, the first in a two-part series, reviews the manipulation commands of PowerPoint and briefly describes their advantages and limitations.
CONCLUSION. The 2002 version of PowerPoint has many useful image-manipulation features. The second article will discuss some practical applications of these features.
Over the past decade, scientific presentations have become increasingly electronic. PowerPoint (Microsoft) is the most widely used program for preparing electronic presentations, more than 95% of which are produced using PowerPoint [1]. In the field of radiology, PowerPoint electronic presentations are replacing the traditional 35-mm slides to a large extent [2]. Most radiology presentations include large numbers of digital images. In most cases, digital images require manipulation and editing after being imported into the PC. Digital image manipulation can be performed using many commercially available software programs, some of which have been discussed in the literature [3–6]. In addition, several articles have described the steps that are essential to prepare PowerPoint presentations [7, 8]. The 2002 version of the PowerPoint program has many helpful image-manipulation features [8, 9]. Mastering these features (for example, through extensive and judicious use of the program Help) enables the user to enhance a presentation by adjusting previously manipulated images. Moreover, in certain instances, the features provide an alternative to dedicated image-editing programs. This article reviews the image-manipulation commands of PowerPoint and discusses their advantages and limitations. The second article will discuss some of the practical applications of PowerPoint image-manipulation features.
Incorporating Images into a PowerPoint Presentation
Before discussing PowerPoint image manipulation, I would like to summarize the basic steps used in producing an image slide with PowerPoint. These steps have already been discussed in detail [8, 9], so they will only be reviewed briefly here.
The easiest method for adding an image is to use the Insert Picture button
from the Drawing toolbar. If this toolbar is not displayed, use View 
Toolbars to select it. After clicking Insert Picture, locate and select the
image by browsing the Insert Picture dialog box. Then click Insert (on the
Insert Picture dialog box), or double-click the image icon itself to embed the
image in the slide (Fig. 1).
Another way to add an image is to use the Insert menu. On Insert, point to
Picture and then click From File (Fig.
2). The Insert Picture dialog box will appear. Locate and select
the image you want by browsing this dialog box. Then click Insert or
doubleclick the image icon. An inserted image will be placed in the middle of
the slide. Click on the image and position the mouse pointer over one of the
corner handles to resize the image.
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To decrease or increase the size, drag the mouse toward or away from the center (Fig. 3). Three points must be emphasized about resizing. First, to maintain the central position of an image, hold down the Control key (CTRL) while dragging the mouse. Second, to maintain width-to-height proportions and to prevent distortion, the use of side handles should generally be avoided in most radiologic images. Finally, to resize an image to an exactly specified height and width, use the Format Picture button (discussed later in this article). After inserting and resizing an image, move it to a desired position by clicking inside the image and dragging the mouse.
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The Picture Toolbar and Image-Manipulation Commands
The Picture toolbar appears by default after an image has been inserted or
selected (by clicking) (Fig.
4). If the toolbar is not displayed, use the View menu to select
it (View Toolbars Picture)
(Fig. 5). The Picture toolbar
has 14 editing commands available in the 2002 version of PowerPoint, but
earlier versions lack some or most of them. The function of each command will
be explained. A general discussion of editing techniques and their practical
applications is covered in the next article.
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Insert Picture allows the user to insert a new image, using the steps just described for inserting a picture from the Drawing toolbar. Color changes the color mode of an image. After selecting an image, click Color, and choose an option from the pull-down menu. The menu comprises Automatic (original settings), Gray Scale, Black & White, and Washout. Gray Scale is the most helpful option in radiology presentations.
More Contrast, Less Contrast, More Brightness, and Less Brightness adjust
the contrast and brightness, respectively, of an image. To change contrast or
brightness, select the image by clicking it. Then click the appropriate button
(e.g., More Contrast) for the effect desired. Repeated clicking increases the
effect on the image. A change can be reversed using Edit Undo or using
the opposite function (e.g., Less Contrast).
Crop removes unwanted vertical or horizontal edges. To crop an image, select the image, and click Crop on the Picture toolbar. The shape of the side and corner handles will change (Fig. 6). Position the cropping tool over the appropriate cropping handle, and drag it inward. To perform equal cropping on two sides simultaneously, hold down CTRL while dragging the handle inward. To turn off the Crop command, click the slide outside the image, or click Crop on the Picture toolbar.
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Rotate Left rotates an image 90° counter-clockwise. To rotate an image, select it, and click Rotate Left. Other forms of rotation (Rotate Right and Free Rotate) and flipping (Flip Horizontal and Flip Vertical) are available on the Drawing toolbar (Fig. 7).
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Line Style adds a frame around an image. After selecting the image, click Line Style, and select one of the options from the pulldown menu. The frame can be customized by selecting More Lines from the menu.
Compress Picture reduces image resolution to 96 or 200 dots per inch or discards hidden portions of a cropped image. Compression is helpful in reducing the file size. To compress an image or group of images, select the images, click Compress Picture, and choose from the options in the Compress Picture dialog box (Fig. 8).
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Recolor Picture can be used only for drawn pictures (vector-based graphics). Radiologic images are bitmapped graphics, so this command need not be discussed.
Format Picture enables the user to apply fine adjustments in image size,
position, line style, brightness, contrast, and cropping. The previously
described Color, Free Rotation, and Compression commands are also available in
Format Picture, which also allows certain effects such as resizing and
cropping to be reversed individually. To format, select the image, and click
Format Picture. A dialog box with multiple tabs will appear. The tabs include
Colors & Lines, Size, Position, Picture, Text Box, and Web. Select the
appropriate tab to adjust or modify features. For example, to restore the
original dimensions of a resized image without reversing other changes, click
Size Reset. The Lock Aspect Ratio box should be checked in radiologic
images.
To make a fine adjustment in contrast, click the Picture tab, and then change the settings. The Picture tab can also be used to restore a cropped image: Click the tab, and then click Reset; or reset the numbers to zero.
Set Transparent Color is used to designate a transparent color in an image. To set a transparent color, select the image, and click the Set Transparent Color button. Click the color that is to be made transparent. Bear in mind, however, that most apparently uniform colors in medical images (e.g., image background) have subtle differences in pixel values. Such differences may create inhomogeneity and noise in the areas in which color was removed. Also, color replacement affects all pixels with the same selected color. As a result, color may be inadvertently removed from additional areas. For these reasons, the Set Transparent Color command has few practical applications in radiology presentations.
Reset Picture reverses all changes that have been made to an image and restores its original state. To reverse not all, but only specific changes, click the Format Picture button on the Picture toolbar. (Note, however, that some options in the Compress Picture dialog box— e.g., Web/Screen and Print or Delete cropped areas of pictures—are irreversible.)
Additional Image-Editing Features of PowerPoint
PowerPoint offers additional image-editing features, such as adding arrows, captions or text, and geometric shapes. These editing features, available on the Drawing toolbar, can be discussed only briefly (Fig. 9). Details are beyond the scope of this article.
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Adding Arrows
To add an arrow, click the Arrow command. Click the area where the arrow is
to begin and drag the cursor in the desired direction for the desired length.
To change arrow style, click Arrow Style on the Drawing toolbar and click a
selected style. Arrow size and color can be customized by right clicking on
the arrow and selecting Format AutoShape or by clicking Arrow Style and
selecting More Arrows. Arrow length and direction can be modified by dragging
the beginning and ending handles.
Adding a Caption or Text
To add a caption or text to an image, click Text Box on the Drawing
toolbar, click on the image, and type the text. The text box can be moved by
dragging it. Text font, size, and color can be adjusted by right clicking on
the text box and selecting Font option.
Adding Geometric Shapes
Geometric shapes (e.g., rectangles or circles) can be used as background
for text or numbers, or as covering for unwanted marks and text on an image.
To add a geometric shape, click AutoShapes on the Drawing toolbar, then point
to a category, and select the desired shape. Next, click on the place where
the shape is to be inserted. To adjust the size of a shape, click on it, then
position the mouse pointer over one of the corner or side handles, and drag
it. The lines and colors of a geometric shape can be customized by right
clicking on the shape and selecting Format AutoShape. To type text in a shape,
click Text Box on the Drawing toolbar, then click inside the shape, and type
the text. To hide unwanted marks or text from the image, place a rectangular
shape on top of it and adjust the size by dragging the handles. The color of
the rectangular shape can be adjusted to closely match the surrounding color:
Right click on the shape, select Format AutoShape, and change the color.
Advantages of PowerPoint Image-Manipulation Features
The advantages of using PowerPoint image-editing features can be considered under two categories: enhancement and manipulation of edited images, and manipulation of unedited images.
Enhancement and Manipulation of Edited Images
In most cases, uniform standards cannot be realistically expected for the
image-editing outcome (e.g., degree of cropping, brightness, or contrast).
Several reasons account for this. First, images of interesting cases are
collected over long periods of time and under different conditions. In
addition, the images presented are frequently obtained from different sources
such as digitizers, digital cameras, and PACS and edited for different
purposes (publication, electronic presentation, Web applications, and so on).
These factors affect the harmony of slide presentations and the uniformity of
slides with multiple images. PowerPoint image-manipulation commands can
enhance a presentation by moderating or eliminating such qualitative
differences. Accordingly, the program provides a practical and time-saving
alternative to reediting images using special image-manipulation programs. In
addition, reediting and saving changes to a compressed image (e.g., a JPEG
file) may degrade image quality.
PowerPoint also enables a user to manipulate an image without altering the stored image or creating a new image. For example, one can emphasize a specific area in an image by cropping or adding text or arrows, enhance the visualization of certain elements in the image, adjust the size and resolution of an image, and show only parts of images to manage space in slides with multiple images. Finally, for relatively small images, the quality of added text and arrows in PowerPoint is superior to those created in image-manipulation programs.
Manipulation of Unedited Images
Unquestionably, using image-manipulation software to edit imported unedited
images before incorporating them into slides has many advantages.
Nevertheless, PowerPoint image-editing commands can substitute for these
programs in certain circumstances. For example, some workplaces may lack these
programs, or time to prepare a presentation may be limited, as may be the case
if a user is unfamiliar with more complex professional programs.
Limitations of PowerPoint Image-Manipulation Features
PowerPoint image-editing features have three major limitations and disadvantages. First, certain functions and tools found in image-manipulation programs are not available in PowerPoint. Some examples include selection tools (e.g., magic wand), paint or air-brushes, rubber stamps, eyedroppers, filters (e.g., sharpening tools), curves, and color balance. Second, images cannot be cropped if they were rotated to an angle other than 90°, 180°, or 270°. In image-manipulation programs, crooked images can be rotated and then cropped. In PowerPoint, cropped margins parallel the rotated margins of the image, not the vertical margins of the slide. However, this problem can be solved through an approach to be discussed in the second part of this article.
Finally, the user cannot change an image file format (for example, from TIFF to JPEG) to further reduce the size of the image.
Conclusion
The 2002 version of PowerPoint has many useful image-manipulation features. This article reviewed the manipulation commands of PowerPoint and their advantages and limitations. The second article will discuss some of the practical applications of these manipulation features.
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