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Development Corner: Image Formats

by Sally Cox  

When it comes to adding images to websites, PowerPoint presentations, or eLearning projects, you will likely be given JPEGs, GIFs, or PNGs. Let's review the three most common image formats and why/when to use them.

JPEG

JPEG is short for "Joint Photographer's Experts Group." It is one of the most popular formats used on the web and in eLearning. JPEG compression (the act of making the image as small as possible while retaining as much quality as possible) is "lossy" compression, which means every time you save an image as a JPEG, it loses quality.

 

The first image above is a JPEG taken with my iPhone. In the second image, I have opened the file in Photoshop and zoomed in on the child's face.

 

 

 

  

 

The little squares you see in the closeup image are called "pixels." Every time you save an image as a JPEG, it loses some quality by throwing out pixels. So if you are editing an image in Photoshop, always save it as the native format first, which is a PSD (Photoshop Document).

 

In the Save As dialog box in Photoshop, choose "Photoshop" as the file format. This saves as a PSD and preserves all details. Then after you finish your edits, do another Save As and choose "JPEG." The original PSD remains fully intact.

 

The image below is an example of the same photo saved multiple times as a low-quality JPEG. Notice that that there is a squarish effect happening and details are lost. This effect is known as "JPEG artifact."

 

 

 

JPEGs use the "RGB colorspace," which has more than 16 million colors. This allows for beautiful continuous-tone images with fluid gradations and a full range of colors. It's a good choice for continuous-tone, but does not allow transparency or animation.

GIF

The "Graphic Interchange Format" (GIF) works in the "Indexed colorspace," so its color palette is quite limited--just 256 colors. GIFs do, however, support transparency and animation (the once-hated animated GIF is making a comeback; I see it every day on Facebook). The oldest format on the web (created in 1989), GIFs are saved as "lossless" compression.

In the image below, I have saved the image as a GIF and it contains just 256 colors. You can see that the image has lost some of its detail.

 

 

Here is an example of an image containing just 8 colors--all detail is gone and the image has a "posterized" effect.

 

 

 

GIFs are perfect for "flat color," i.e., logos or flat design graphics that don't have gradations or continuous-tone (remember: only 256 colors). 

 

PNG

 

The "Portable Network Graphic" was created (approved as a web standard in 1996) to provide high quality continuous-tone but also allow for transparency and animation.

PNGs are saved in the RGB colorspace, so they have the full range of 16 million+ colors. What I like best about PNGs is the ability to save transparency, which I use every day in my workflow. I save my graphics as high-quality PNGs and allow transparency (a checkbox I choose in Adobe Illustrator when I export a graphic to PNG).

In a recent project I wanted to use an image of a headset, and I needed the background to be transparent. I opened the image in Adobe Illustrator and set the Export PNG options to High Quality and set the Background Color to Transparency.

 

 

 

Thanks to the Transparency option, I had the freedom to overlay the headset on the green background shown below.

 

To Recap:

	JPEG	GIF	"PNG"
COLORS	16 MILLION +	256	16 MILLION +
TRANSPARENCY	NO	YES	YES
ANIMATION	NO	YES	YES
CONTINUOUS-TONE	YES	NO	YES
FLAT COLOR	NO	YES	YES

 

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Adobe InDesign: Nested Styles

by Mira Rubin  

If you've spent any amount of time working with Adobe InDesign, you probably know how to create Paragraph and Character styles. Nested styles take Paragraph styles to a whole new level with complex formatting you can apply with the click of a button. Nested styles are ideal when the paragraphs being formatted follow a consistent pattern such as entries in a catalog, directory, or bibliography.

Let's take the example of a contact list, where each entry is a paragraph with the following elements in common:

Last name, First name: (Phone Number Exchange) Phone Number

 

In this example, the paragraph structure is an assemblage of modules separated by markers--the comma between last name and first name, the colon before the phone number and the parentheses around the number exchange. You can apply different formatting to the modules using the markers as transition points. The trick to nested styles is to first create character styles that capture the variations in formatting. The character styles are then assembled to build a super smart paragraph style.

 

The example we'll use employs four variations in formatting. The phone number itself will be captured in the foundation paragraph style and the other three formats will be captured as character styles.

 

 

 

To begin, set up the paragraph so the last name, first name, number exchange and phone number all have distinct formatting. Be sure to include the comma, the colon, and the parentheses around the phone number exchange.

With the Type Tool cursor positioned in the last name, choose Window > Styles > Character Styles. When the panel opens, hold the Alt key (Windows)/Option key (Mac) and click the Create new style button at the bottom of the panel.

 

When the New Character Style dialog opens, name the style lastName. Notice the summary of formatting properties in the Style Settings section of the dialog.

 

Click OK to close the dialog.

Repeat the process and create character styles that capture the formatting of the last name and the phone number exchange (name the styles accordingly).

 

Now comes the fun part--assembling the paragraph style from the character style components.

Because InDesign captures paragraph properties from the formatting of the text at the cursor location, position the Type Tool cursor in the main phone number text. Choose Window > Styles > Paragraph Styles and, when the panel opens, Alt+Click/Option+Click the Create new paragraph style button at the bottom of the panel. Name the style listing.

Click the Drop Caps and Nested Styles category at the left of the New Paragraph Style dialog to display the nested styles options.

Click the New Nested Style button, then click the drop-down menu to the right of the word None in the first text field. Choose lastName from the list of character styles.

You want the last name and the comma following it to have the same formatting so, ensure that through is selected in the second column of options.

Select the word Words in the third column, and press the comma key on your keyboard to enter the comma as the delimiter.

Click the New Nested Style button again, this time assigning the firstName style and a colon as the delimiter.

Click the New Nested Style button a third and final time and assign the exchange style with a closing parenthesis as the delimiter. (Click OK to complete the style and close the dialog.)

 

To use the style, select the paragraphs you want to format and click the style name in the Paragraph Styles panel.

Whether it be one paragraph or a thousand, as long as the paragraphs in your document are uniformly structured, nested styles make it possible to apply complex formatting reliably and consistently at the click of a button.

 

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