(819k)Grech V*. Publishing on the WWW. Part 6 - Simple
graphic manipulation. Images Paediatr Cardiol 2002;9:55-68
*
Editor-in-Chief, Images Paediatr Cardiol
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(819k) |
Grech V*. Publishing on the WWW. Part 6 - Simple
graphic manipulation. Images Paediatr Cardiol 2002;9:55-68
|
|
*
|
Editor-in-Chief, Images Paediatr Cardiol
|
| Internet | Publishing | Medical illustration |
Article
This article will demonstrate, step by step, how images are processed
by Images in Paediatric Cardiology, and made suitable for on-line publishing.
I will do this by illustrating with actual work done on graphics that have
been published in the Journal. The software used is Paint Shop Pro 7, a
graphic manipulation program by JASC software.1 We will start
with the graphic as submitted to the journal, and the end result will be
a graphic that is suitable for publication online. Such a graphic should
be clear, informative and small enough in file size to allow easy download
in a web page article at the user end i.e. up to 20K.
Image acquisition
Images are sent to the journal on removable media (usually floppy or
CD), or as email attachments. Such images may be sent as separate graphic
files or may be embedded in a document, usually in a word processor file
such as Microsoft Word, or perhaps as a graph in a spreadsheet.
Stand-alone files may come in one of several formats. The most commonly
used format is JPG ('Joint Photographic Experts Group').2 However,
up to date graphic editing software will be able to view and modify virtually
any of the common (and not so common) file formats. The JPG format employs
a compression algorithm that allows files to be reduced in size and thereby
become more easily downloadable from the internet. The JPG standard available
in the public domain supports sixteen million colours, and hence displays
continuous tone images (such as photographs) very well. However, the compression
used is lossy, that is, data considered not essential by the compression
algorithm is discarded, mostly by averaging pixel values to those pixels
in its immediately surroundings. The compression level is under the operator’s
control (see below) but excessive compression will result in loss of detail
and the creation of artifacts.3 At lower compression levels
(approximately <20%), the output image is virtually indistinguishable
from the original. A JPG file is processed in the following steps:
| The original file in JPG format (755 by 708 pixels - 32.8K) is too large in physical dimensions to be shown on this page but can be viewed by clicking on the above link. Figure 1 shows the original graphic resized to fit this page. |
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| Some scratches are visible and these can be removed with the scratch removal tool as shown in figure 3. |
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| Various settings may be employed and the before and after results are shown in the two windows in figure 4. |
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| The creation of a file in JPG format results in a variable degree of JPG artifact. This artifact is akin to a halo surrounding the sharp parts of the image, and was produced when the graphic was first created and saved in this format. The artifact should be removed at this stage. The menu steps to remove the JPG artifact are shown in figure 5. |
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| The JPG artifact removal dialog box is shown in figure 6. This step incidentally also results in the removal of many of the remaining scratches. |
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| The graphic is now cropped, removing areas that are not useful. Since the overall size will now decrease, the file size will also decrease. The area selection tool button is shown in figure 7 (see arrow). The area of interest is selected (figure 8) and the menu used to crop to the selection (figure 9). The end result is shown in figure 10. |
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| This graphic is still too large to be seen comfortably on screen at 603 by 587 pixels, and should be resized to 400 by 350 pixels at most (width and height respectively) so as to ensure that the final result will be easily visible on all monitors with screen set resolution down to 640 by 480 pixels. Instructions on screen resolution settings are available in another section of the journal. The image is resized to 360 by 350 pixels by using the menu shown in figure 11 |
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| The image size settings dialog box is shown in figure 12. |
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| Since this graphic is an x-ray, it should be in a grey scale of colours, shading from absolute white to absolute black. This is easily done by using the colour menu (figure 13). |
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| The result is shown in figure 14. |
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| Text displaying journal copyright is now added. The text tool is shown in figure 18 (arrow). This menu brings up the text dialog box (figure 19). The necessary text is typed and formatted and is then moved in the picture to the required site. |
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All that remains is to output the final graphic for publication purposes.
This can be done through the JPG optimiser facility (figure 20), which
brings up the optimiser dialog box (figure 21). As can be seen, 14% compression
produces a very acceptable final image that is just under 20K in size (figure
22). It is possible to produce JPG images that are progressively encoded
i.e. the journal readers’ browsers display the image gradually as it is
downloaded, using a series of scans to provide increasingly detailed versions.
However, progressive JPG downloading requires more computer memory and
is not supported by all web browsers.
Images on the internet may also be found in a format called GIF (Graphics Interchange Format), and this format is non-lossy.7,8 However, this format only supports a maximum of 256 colours and is therefore used for simple line images or when the image background needs to be kept transparent.3
If the image sent for publication is embedded in a document, the image can be extracted into the graphic manipulation software in one of several ways. It can be selected in the document, and then copied and pasted into the graphic manipulation software. If this is not possible, or if the resultant graphic is suboptimal in quality, then the graphic can be captured by viewing it in the original document, and the entire page then captured by pressing the ‘printscreen’ button on the keyboard. This keypress pastes the entire screen to the clipboard. This large graphic is then pasted into the graphic manipulation software and the actual image only cropped. Yet another option, if available, is to open the original document and to save it in hypertext format. The current versions of Microsoft Office, for example, will readily do this. The resulting web page will have links to freshly created graphics, created from the original graphics embedded in the document. The disadvantage of this option is that no control is available over compression levels etc.
Scanning printed images can produce unwanted patterns (figure 23). The
Moiré patterns removal feature can remove this (figure 24).6
In conclusion, modern graphic manipulation software is quick and simple to use, and allows medical quality graphics to be produced for online publication.
References
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