52. Save an Image in PNG Format
Before You Begin
47 About Saving Images
As you learned in 47 About Saving Images, the PNG file format is compatible with certain Web browsers, but not all. Because it isn't uniformly accepted as a Web format, you might not want to use PNG images on your Web site. PNG format, like GIF and JPEG formats, offers a variable amount of compression, depending on the choices you make. Unlike JPEG, PNG offers a lossless compression method. Like GIF, PNG offers transparency, but unlike GIF, PNG supports alpha transparency.
PNG format follows two compression schemes: PNG-24 and PNG-8. Both formats are lossless, but PNG-8 increases compression by reducing the number of colors an image displays onscreen. PNG-8 format is similar to GIF, and requires you to select the optimal color palette for best display. PNG-8 files are typically much smaller than GIF files. PNG-24 files are similar to JPEG but larger; however, PNG-24 files use lossless compression which JPEG files do not.
Because transparency is one of the features not universally supported by Web browsers, you might not want to use transparency in your PNG image. In particular, the alpha channel in a PNG file allows you to store pixels of varying degrees of transparency regardless of color; however, this feature is not supported by Internet Explorer.
Choose File, Save As
In the Editor, open the file you want to convert to PNG format. The file is probably a PSD-formatted copy of an image to which you've already made changes. Then choose File, Save As from the menu bar. The Save As dialog box appears.
Choose PNG Format
From the Format drop-down list, choose PNG.
Select Save Options
Select options as needed. For example, to save the PNG copy in the catalog and add it to the version set that includes the edited PSD copy and the original file, enable both the Include in the Organizer and Save in Version Set with Original check boxes. See 47 About Saving Images for help in selecting other options.
If desired, change the filename displayed in the File name box. Normally, you do not have to do this because the file will automatically have a different file extension than the original file (the file extension changes because you've chosen a different file type).
Click the Save button. If you see a note reminding you that you're saving this image as part of a version set, click OK to continue. The PNG Options dialog box appears.
Set How Image Should Appear and Click OK
In the PNG Options dialog box, choose how you want the image to appear on a user's system when it's downloaded from the Web. To have the PNG file appear one line at a time from the top down, select Normal. To have the image appear in several cycles, with details filled in gradually, select the Interlaced option.
The method shown in this task results in a PNG-24 file. To compress the file even more using PNG-8 format, choose File, Save for Web to display the Save For Web dialog box. You'll find options for selecting an 8-bit color palette, along with tools that allow you to zoom in and out, compare the original and the compressed image side by side, and preview the image in your Web browser. If you use the Save for Web command, however, you will not be given an opportunity to save the file in the Organizer or create a version set with the original image. For help in selecting a color palette and choosing other options related to PNG-8, see 63 Change Color Mode.
Click OK to convert the image. If the As a Copy option was enabled in the Save As dialog box, your original PSD file is still open; the PNG copy is saved to disk and closed automatically. Click Save on the Shortcuts bar to make sure that your final edits are preserved in the PSD file, then click the Close button on the PSD image to close it as well.