Working with GIF files
Corel PaintShop Pro lets you optimize GIF files to maximize quality while minimizing file size. You can save images with or without transparency, depending on how you want to display them on your Web pages.
Paletted images (those with 256 or fewer colors, such as GIF or PNG files) do not support transparent backgrounds, but you often need to make part of your image transparent for a Web page. For example, you may have a round logo and want to display the background of the Web page around the logo. In this case, you can choose not to display one color. Most Web browsers support this option, effectively making that color transparent.
The GIF Optimizer dialog box contains four tabbed areas in which to configure the transparency, color, and format options of the file. The fifth tabbed area displays estimated download times of the image at various modem speeds.
GIF Optimizer Transparency
You can choose to base transparency on existing image or layer transparency, or you can sample a color in the image that you want to make transparent. If you have a selection in your image, you can base the transparency on the selection.
GIF Optimizer Partial Transparency
A GIF file cannot contain partially transparent pixels. All pixels must be either transparent or opaque (visible). Original images may contain partially transparent pixels if the image does not have a background layer, and you have reduced the opacity of a layer, added a mask, feathered a selection, or used a brush at a reduced opacity setting. You can determine whether the partially transparent pixels become transparent or opaque, and whether they are blended with another color.
Important! If you mark the None option under the Transparency tab, the options in this area are unavailable.
GIF Optimizer Colors
GIF images have an 8-bit color depth, which means they can display up to 256 colors. Because these colors are stored in a palette, an image containing 256 or fewer colors is called a paletted image. To reduce file size, you can have fewer than 256 colors. You can use the options under this tab to select the number of colors and the type of palette used.
GIF Optimizer Format
GIF images can be interlaced or non-interlaced, which affects how the image is displayed on a computer with a slow Internet connection. You can also save the image to an older version of the GIF format to enhance compatibility with older applications.
GIF Optimizer Download Times
The Download Times tabbed area in the GIF Optimizer dialog box displays the size of the compressed file and estimated download times for four different Internet speeds. If the file size is too large, you can decrease it by reducing the number of colors.
Using the Transparent GIF wizard
You can open the Transparent GIF wizard from the GIF Optimizer dialog box. This wizard guides you through the steps of optimizing a GIF file.
What is interlacing?
Interlacing is a method that lets you display a Web-based image on the screen at a low, blocky resolution. As the image data loads, the image quality improves.
To optimize and save a GIF file
Edit workspace
1 Choose File Export GIF Optimizer.
The GIF Optimizer dialog box appears, and the preview areas show the current image on the left and the resulting GIF file on the right.
2 Click the Transparency tab, and choose one of the following options:
• None — produces a GIF file that does not use a transparency setting
• Existing image or layer transparency — uses the current transparency information from the image
• Inside the current selection — for images with a selection, makes everything within the selection transparent
• Outside the current selection — for images with a selection, makes everything outside the selection transparent
• Areas that match this color — bases the transparency on a color you select. Click the color box to select a color or choose a color from the image by moving the cursor over the image, and clicking a color. Then set or type a tolerance factor in the Tolerance control to determine how closely colors must match the selected color before they become transparent.
3 Click the Partial Transparency tab and choose one of the following options:
• Use full transparency for pixels below x% opacity — determines the opacity value at which pixels become transparent. Pixels below the opacity value you set become transparent. Pixels above the opacity value become opaque. As you lower the value, you reduce the number of transparent pixels.
• Use a 50% dither pattern — makes partially transparent pixels opaque using either the color chosen for blending or the image color (depending on the blending option), then applies a 50% dither pattern to make colors look more natural
• Use error diffusion dither — makes partially transparent pixels opaque using either the color chosen for blending or the image color (depending on the blending option), then applies an error diffusion dither to make colors look more natural
4 Choose one of the following options to determine how partially transparent pixels are blended:
• Yes — blends the partially transparent pixels with the color in the Blend color box. To choose a new color, click the color box, and choose a color from the Color dialog box. Partially transparent pixels below the value you set above are blended with this color.
• No — uses the existing image color at 100% opacity
5 Click the Colors tab, and type or set a value in the How many colors do you want? control to determine the number of colors you want in the image.
Note: As you remove colors, the size of the file decreases, but so does the quality of the image. Use the preview areas to help you determine the best balance between file size and image quality.
6 Type or set a value in the How much dithering do you want? control.
The range is 16 to 256 colors. This determines the way Corel PaintShop Pro arranges pixels in an image to compensate for missing colors in the adjacent pixels.
7 Choose one of the following options to determine the image palette:
• Existing Palette — lets you use an existing image palette
• Standard/Web-safe — lets you use the Web-safe palette for images that you want to use on the Web
• Optimized Median Cut — lets you reduce the image to only a few colors. If you choose this option, you can mark the Boost selected colors check box to give the colors more weight by a factor of the value you set. The selected colors stand out from the rest of the image. To boost colors, make a selection of an area that contains these colors and then mark this check box.
• Optimized Octree — lets you optimize an image that contains only a few colors
Note: Depending on your needs, you may want to try both the Optimized Median Cut and the Optimized Octree options and choose the one that gives you the best results.
8 In the Options group box, mark the Include Windows colors check box to include the 16 standard Windows colors in the palette.
If the image will be used on the Web, mark the check box.
9 Click the Format tab, and choose one of the following options:
• Non-interlaced — produces an image that downloads one line at a time, starting from the top
• Interlaced — produces an image that is displayed incrementally in several passes, and detail is added each time
Note: Choose the Interlaced option with larger images so that the viewer can get an idea of how the image looks while waiting for it to download.
10 Choose one of the following options:
• Version 89a — lets you save transparency information. It is selected automatically if the image contains transparent pixels.
• Version 87a — lets you save an image that does not contain a transparency setting
11 Click OK to open the Save As dialog box, and navigate to the folder in which you want to save the new image and type a name for the file.
12 Click Save.
To use the Transparent GIF wizard
Edit workspace
1 Choose File Export GIF Optimizer.
The GIF Optimizer dialog box appears.
2 Click Use wizard, and follow the instructions.
3 Click Finish to close the wizard and open the Save As dialog box, where you type a name and select a location for saving the GIF file.
You can also | |
Choose a color within the image | On page 1 or 2 of the wizard, move the cursor over the image, and click a color. The color swatch displays the color you clicked. |
Choose a color using the Color dialog box | On page 1 or 2 of the wizard, click the color swatch to open the Color dialog box. For more information about the controls in the Color dialog box, see To choose a color from a dialog box. |
Change a setting | On page 5 of the wizard, click Back to return to the previous pages, change the settings you want, and return to page 5 to view the results. |
A GIF image cannot contain partially transparent pixels. If the image contains them, the Transparent GIF wizard blends them with the color you choose. Reducing layer opacity, adding a mask, feathering a selection, and using a brush set at reduced opacity are some of the actions that can produce partially transparent pixels.
You can click the Download Times tab to preview the file size of the compressed file and view an estimate of the download time at four modem speeds.