optimizing screenshots in FrameMaker for PDF output
I have to include a lot of screenshots in the documentation of my company’s user interface. I want them to be good quality, so that the user can easily read what’s in the screenshot and compare it to what they’re seeing on their monitor. But I’m also sensitive to the size of the resulting PDF. I don’t want users to have to handle a 20-MB PDF file. This means I have to balance the size and quality of the screenshot on the page with the size of the resulting PDF.
I have done a number of experiments with a variety of image formats and a range of dpi values. Here are a few of the things I’ve learned:
• PNG is a good file format for saving screenshots, because the quality of the image file is high. However, PNG is one of those formats that can include compression. So, turn off any compression in your screen capture program. On my program (IrfanView), that means Compression Level 0. The resulting PNG files might be large (1-5 MB), but that doesn’t mean the eventual PDF will be large.
• For some reason, FrameMaker seems to “like” 72 dpi. Not sure why this is. When images are 72 dpi, they seem to come out clearer than other dpi settings. So, when you capture a screen, not only do you save it as a PNG file, but you adjust the dpi of the image to 72 dpi. I know, you want 300 dpi. But you know what? For the purposes of an image on a PDF page, that amount of detail is overkill.
• Capture the screen as close to the size of the eventual displayed image as possible. If the eventual image on the page is going to be 5 inches across, you don’t need a 20-inch image. I wouldn’t go more than 2 times the size of the eventual displayed image.
• In FrameMaker, when you import the image, I suggest “Import By Reference” rather than “Copy Into Document”, for a couple of reasons. First, if you “Copy Into Document”, the size of the FrameMaker file itself gets very large. This doesn’t affect the size of the eventual PDF file, but it can make the FrameMaker file a little unwieldy to save, open, and close. Also, if you “Import By Reference”, you can change the image in the document just by changing the referenced file. For example, suppose you capture an image of a screen and import the image by reference into the document. Then the design team changes the screen slightly. All you have to do is capture the new image and save it with the SAME NAME as the original image file. The image in the FrameMaker file will automatically use the new image file when you open the document. That can save you a lot of time in re-importing the new image.
• In FrameMaker, use the Object Properties pane to adjust the Scaling of the imported image. For example, if you did as I suggested above, the captured image might be 2 times the size of what you want the displayed image to be, so you would use a scaling of 50% to get it to be the right size. I suggest you use scalings that are nice powers of 2. 50% = ½, 25% = ¼, that kind of thing. If you need something in between, again use a multiple of one of these, like 37.5% = 3/8.
• When you generate the PDF from the FrameMaker file, don’t fuss around with the options for image handling in the PDF controls. You’ll only make things worse. If you start with a good quality image, in uncompressed PNG format, at 72 dpi, scaled to the size you want, FrameMaker does a good job most of the time and you should get good results.
By all means, experiment if you want. Perhaps your images work better with another file format, another dpi, and so forth. But these settings have been giving me good results – good quality with a reasonable size PDF – so I’m sticking with them for now.
I have done a number of experiments with a variety of image formats and a range of dpi values. Here are a few of the things I’ve learned:
• PNG is a good file format for saving screenshots, because the quality of the image file is high. However, PNG is one of those formats that can include compression. So, turn off any compression in your screen capture program. On my program (IrfanView), that means Compression Level 0. The resulting PNG files might be large (1-5 MB), but that doesn’t mean the eventual PDF will be large.
• For some reason, FrameMaker seems to “like” 72 dpi. Not sure why this is. When images are 72 dpi, they seem to come out clearer than other dpi settings. So, when you capture a screen, not only do you save it as a PNG file, but you adjust the dpi of the image to 72 dpi. I know, you want 300 dpi. But you know what? For the purposes of an image on a PDF page, that amount of detail is overkill.
• Capture the screen as close to the size of the eventual displayed image as possible. If the eventual image on the page is going to be 5 inches across, you don’t need a 20-inch image. I wouldn’t go more than 2 times the size of the eventual displayed image.
• In FrameMaker, when you import the image, I suggest “Import By Reference” rather than “Copy Into Document”, for a couple of reasons. First, if you “Copy Into Document”, the size of the FrameMaker file itself gets very large. This doesn’t affect the size of the eventual PDF file, but it can make the FrameMaker file a little unwieldy to save, open, and close. Also, if you “Import By Reference”, you can change the image in the document just by changing the referenced file. For example, suppose you capture an image of a screen and import the image by reference into the document. Then the design team changes the screen slightly. All you have to do is capture the new image and save it with the SAME NAME as the original image file. The image in the FrameMaker file will automatically use the new image file when you open the document. That can save you a lot of time in re-importing the new image.
• In FrameMaker, use the Object Properties pane to adjust the Scaling of the imported image. For example, if you did as I suggested above, the captured image might be 2 times the size of what you want the displayed image to be, so you would use a scaling of 50% to get it to be the right size. I suggest you use scalings that are nice powers of 2. 50% = ½, 25% = ¼, that kind of thing. If you need something in between, again use a multiple of one of these, like 37.5% = 3/8.
• When you generate the PDF from the FrameMaker file, don’t fuss around with the options for image handling in the PDF controls. You’ll only make things worse. If you start with a good quality image, in uncompressed PNG format, at 72 dpi, scaled to the size you want, FrameMaker does a good job most of the time and you should get good results.
By all means, experiment if you want. Perhaps your images work better with another file format, another dpi, and so forth. But these settings have been giving me good results – good quality with a reasonable size PDF – so I’m sticking with them for now.
posted by Ed DeJesus at
12:20 PM
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