WEB DEVELOPMENT BLOG

November 14, 2007

A picture is worth a thousand words, but that's not always enough

How to add captions to images in Photoshop

On the Web it is preferable to place your
caption in the HTML. If that won't work and
your captions are long, you should also link
to a place providing a description of the image
and an alternative rendering of the text.

Colleagues of mine are involved in a project that involves adding captions to photographs. Like many of you, they aren't full-time designers and haven't spent a great deal of time using Photoshop. While they know how to crop and resize photos, they've not yet worked with type. For those of you who may someday face the same situation, here is a quick tutorial on adding text to images.

Establish your project parameters—size matters

Are your captioned images going to be used on the Web, on hand-outs produced by your office printer or in commercial print work such as a magazine? At what size will they be used? When editing your photos you will want to start with the largest image file available, crop it as necessary then resize it to your project specifications before adding your text.

As I mentioned when discussing image formats, your usage will impact your size specifications. Generally you will want an image that is 300 pixels per inch (ppi) for commercially printed pieces, one that is 125-250 for desktop printing (refer to your user manual to determine the maximum dots per inch (dpi) your printer will produce) and somewhere around 72 to 100 for the Web.

Note: measurements for print are exact; if your photo is 300 dpi and 1 inch square, it will be printed to be exactly 1 inch square. If you print it at 72 dpi and 1 inch square it will still be exactly 1 inch, but will have less detail. Measurements for the Web are relative because they are determined by your display. On my Dell there are 77 pixels in an inch, while on my Mac there are 98 pixels in an inch. Your display may be different. As a rule of thumb I just use 72 (which was common for most monitors back in the 1990's) and keep in mind the fact that a 3 inch wide photo at 72 ppi will appear smaller on the Mac than it will on the PC. Either way it is 216 pixels, but the pixels on my PC are bigger than those on my Mac.

Consider the amount of text you are supposed to add to the image. Try to make this as brief as possible, especially if your project will be viewed online. While you may be able to use tiny type on printed matter, that type will be harder to read online. Fewer pixels mean fewer details, so 6 point type online will be tiny and jagged.

Also ask yourself if the text needs to be on the picture itself or if it can be read as a caption underneath the image. If the project is for the Web you can include captions underneath a photo in the text rather than in the image. For situations where that won't work, such as HTML e-mail, just be sure to repeat your caption text in the alt tag of the image.

How to add text in Photoshop

For this example I'll walk you through the steps used to caption the image used in this entry. We'll add text on top of the image and below.

1. Open your image file in Photoshop. For practice you are welcome to use this sculpture photo.
2. Resize your photo by going to the image menu and choosing image size. Make sure that "constrain proportions" and "resample image" are checked. Set the resolution appropriate to your project. I'm using 72 for the Web. Choose the appropriate width for your image. I'm using 240 pixels.
3. Click on the foreground color and use the picker to select a color for your type.
4. Select the type tool, click and drag on the image to create your type box, and start typing your content.
5. If it is not already open, go to the window menu to open your layers window. Note that your type was created on a new layer.
6. Switch to the selection tool to reposition your type as desired.
7. If your background is too busy, you may find that your type is hard to read. Try adding a drop shadow or outline to it. To do this double click on the type layer in the layers menu (click to the right of the layer name). This will open up the layers style menu. Check drop shadow, then click on the words "drop shadow" to see your parameters. Drag the menu somewhere to the side—so you can still see your type—then adjust the angle, spread, size and distance until your type looks clear. You can experiment with drop shadow and other options to create different effects. You can also try changing the color. Just try to keep it simple. (Hot pink type with a lime drop shadow is usually a no-no—unless you're competition is "Hello Kitty.")
8. Sometimes a drop shadow isn't enough. In this case you may want to experiment with darkening the background behind the type. You can use the burn tool to just darken an area (paint over your background with this). Another option is to create a rectangular area behind your type that is darker than the rest. To do this, create a new layer above your background image, and create a rectangle with your selection tool. Using the paint can fill it with black. Now you can leave it as is to call greater attention to your caption, or you can adjust the opacity to the layer to make it semi-transparent. In the sculpture photo I've set the opacity of the black square to 50%.
9. If you've tried a few of these options and your type still doesn't look right, you may want to put the caption below, instead of on, the image. If your project is going on the Web you can do this in your HTML. If you are sending an HTML e-mail though you will want to include it in the image file. To do this, you will need to increase the size of the image. First set your background color to be the same as that of your document. In this example I'll use white. Next go to the image menu and select canvas size. Click on the center top square in the grid then increase your height measurement to an appropriate size. I've added .5 inches. Now just add your type to this area. If you've added too much space you can crop accordingly.
10. Save the file in Photoshop format (in case you want to make edits) then go to the file menu and choose "Save for Web." Select JPEG as your file format then click save. If you would prefer a .tif file (for print) you would instead flatten image (under the layers menu) and save as .tif.

Alternative Text for Captions

Captioning images can add value, but will also pose accessibility challenges. If your caption is short, you should copy it into the alt tag of your image. This will make it available to those who use screen readers or other user agents that don't show images. If your caption is too long, you may also want to link to an alternative copy of the text, either on the same page, as a footnote, or wherever you deem appropriate. Read Andy Clarke's article, Accessible alternatives, to learn more about these techniques. For this example I've linked to a description of the image and text and placed it here on the page:

Photograph of part of a sculpture featuring a man holding an umbrella next to a dog whose nose is pointed at the mans's knee. Captions built into the image read as follows:

• Spot, can't you find a squirrel to chase? You've been sitting here panting on my leg for years now.
• What, and you think this is my idea of the perfect view?
• This caption is part of the image file, but sits below the picture.

In Conclusion

As you've seen, it's pretty easy to add text to an image. The tricky part is making it look right and ensuring that the content is available to all. But with a bit of experimentation you can accomplish both tasks.

Stumble It!

Posted by: Heidi Cool November 14, 2007 05:44 PM | Category: Accessibility , Content , Heidi's Entries , How-to , Tips and Tricks , images

Posted by: hac4 (Heidi Cool) November 14, 2007 05:44 PM | Comments (9) | Trackback

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