As of version 5 and later, Photoshop includes a very helpful "Save for Web" command. This element enables you to save a copy of your image that is optimized for internet use. "Optimized" means that the image file will be as small as possible, and that the image will use only Web-safe colors. The "Save for Web" option can save images in GIF, JPEG, or PNG format.



Using Save for Web When you're ready to put your image in your web page, from the File menu select "Save for Web". The "Save for Web" dialog appears:

This is where you tell Photoshop how you'd like to optimise your image for the Web. You can select the file format to produce (GIF, JPEG or PNG), what size palette you'd like to use, how to cut down the colours to fit the chosen palette size, how much to dither the optimised image (if at all) and how much to sacrifice image quality to produce a smaller file size.

Image views You will see four tabs above the image view pane on the left. These panes allow you to view the original image, the optimized version, the original and optimized versions side-by-side ("2-Up") and the original, optimized and two variations on the optimization all together ("4-Up"). You can also use the Hand tool on the top-left to move the view around, the Zoom tool to zoom in and out of the image, and the Eyedropper tool to select a color from the image.

Presets There are many options in the Save for Web dialog, and the choices here can be quite bewildering! Fortunately, there are lists of presets you can choose from to make it easier. Select the Settings: drop-down list, which is located just below the Cancel button, to bring up the list of presets:

In the presets there are three basic image formats - GIF, JPEG and PNG. As a basic rule you use JPEG's for photos and GIF's for everything else. For a complete lesson on selecting the right image format, see Understanding image formats.

Optimising GIFs If you're making a GIF, start off with a preset such as GIF 32 Dithered, which should work well for most GIFs. You can then fine-tune the optimisation to suit your needs. Some of the important optimisation options are discussed below.

Color reduction method This is the drop-down box located below the Image Format box. The most frequently used options here include:

Perceptual: Creates the reduced color palette which favors colors that the human eye is more sensitive to. Selective: Like Perceptual, however better for Web work. Selective is the favored (and default) option. Adaptive: Creates the palette by taking an even sampling of colors from the image's color spectrum. This is generally not as good a choice as Selective. Web: Use this if you need a complete Web-safe color palette (Netscape 216-color palette). These days, this method usually isn't that important as most computer displays support at least 16 million colors. Dithering method This is located below the "color reduction method" box. Dithering involves adding patterned or random dots to the image to make it appear to contain more colors than are actually in the palette, allowing you to use a smaller palette size. The options are:

No Dither: No dithering is applied to the image. Good if the dithering effect looks bad, but can produce severe "banding" of colours. Diffusion: Uses error diffusion dithering, which looks similar to Noise dithering, producing a random-looking pattern of dots. Can produce seams when using ImageReady slices. Pattern: Uses a pattern for dithering, rather than random dots. Can work well for some images, but often produces a rather artificial look to the image. Noise: Similar to Diffusion, but does not produce seams at the edges of slices in ImageReady. Transparency This checkbox is only available if your image does not have its Background layer turned on. It specifies that you want parts of the saved GIF to be transparent. If you deselect this checkbox, the transparent areas will instead be filled with the Matte colour (or white if no matte is selected).

Interlaced A quick note about this: if checked it does increase the file size. This checkbox controls GIF Interlacing. If enabled, the GIF will appear gradually as interlaced horizontal lines as it is loaded on the Web page, which gives viewers something to look at while the full image appears.

Lossy If you wish to reduce the file size further this slider allows you to remove detail from the image. Use this only if you don't mind reducing the image quality quite severely! A value of 0 will not remove any detail; a value of 100 will remove the maximum amount of detail.

Colors This is where you can select the size of your GIF palette. A palette of 32 colors is often sufficient for web images, but if your image has a lot of detail and looks too fuzzy/blurry/banded with 32 you can bump it up it to 64, 128 or 256. If your image has very few colors in to start with, or doesn't look too bad with fewer colors, select 16, 8, 4 or even 2! This will make the GIF file size smaller.

Dither If you have chosen a dithering method (see above), this option will allow you control over how much the image is dithered - 0 means no dithering, 100 means lots of dithering.

Matte The matte is the background colour you want to use for your image. If you've enabled Transparency (see above), then the foreground image will be faded at the edges to blend in with the matte colour. If you choose the Matte setting of None, the GIF will have a "hard transparency" with no fading; this is great if you want to be able to use the image on any colour background.

If you've disabled Transparency, the transparent areas of your image will be filled in with the matte colour.

Web Snap If you want to use web-safe colors you will want to increase the Web Snap slider. Photoshop will bias your color palette more and more towards web-safe colors the higher the value of Web Snap.

Optimising JPEGs If you're making a JPEG, start off with a preset such as JPEG Medium, which should work well for most JPEGs. You can then fine-tune the optimisation to suit your needs. Some of the important optimisation options are discussed below.

Quality There are two ways to modify the quality of the compression: the Low/Medium/High/Maximum list, and the Quality slider (for fine control). The lower the quality setting, the more blurry and bitty the JPEG will appear, but the smaller the resulting file size.

Progressive A progressive JPEG is similar to an interlaced GIF. The image loads gradually on the Web page - a low res image first and then the full, high-resolution image. Again, this is great for keeping your viewers on slow modems from getting bored, but it does mean a slightly larger file size. Please note that older browsers don't support progressive JPEGs.

Matte If your Photoshop image has transparent areas, you can fill them with a specified matte color with this drop-down box.

Optimizing PNGs Your options for optimizing a PNG-24 are much the same as those for optimizing a JPEG. Similarly, the options for optimizing a PNG-8 are very similar to those for optimizing a GIF. See the GIF and JPEG sections above for details.

If you really can't be bothered... ...you can always let Photoshop optimise your image for you! Select the little arrow just to the right of the Settings... box and select Optimize to File Size...:

In the dialog that pops up, select Auto Select GIF/JPEG then enter your desired file size. Click OK and Photoshop does the rest for you! If you're not happy with the results, tweak the settings as described in the sections above, or just choose a slightly larger file size and try again.

Saving the image Once you're happy with your optimised image, click OK to save it to disk. The file saved will be a copy of your original image, unless you specifically overwrite the original with the optimised file.