PNG - Export

Portable Network Graphic Format (PNG), pronounced "ping" is a bitmap file format. It is specifically designed for network image data transmission and storage. It is capable of loslessly storing bi-level to 48 bit true color image data. PNG is a well-designed and well-developed file format that is intended to replace CompuServe's GIF file format.

PNG is a newer format that provides inclusion of transparency with a 16 bit alpha channel. EazyDraw and OS X support color transparency. For this reason you may find PNG to be the preferred interchange format for web, network, and computer display applications. This may become more important as more applications add support for transparency. PNG also provides a faster progressive display interlacing scheme than GIF. PNG does not support multiple images per file that are used for storage of animation sequences.

The Dots Per Inch (DPI) parameter is used to define the resolution or quality of the exported representation. Normal display screen viewing requires about 72 DPI for acceptable visual quality. Printed applications usually require 300 DPI for good quality representation. High quality printed results may need 600 DPI or greater.

The middle popup menu provides a selection to export just the visible graphics and text, or the entire drawing. This directly effects the size of the output file and how the resulting PNG bitmap will appear in other applications.

There is no choice concerning compression of a PNG file. Lossless compression is always applied, it is a LZ77 variant of LZW. These algorithms are not encumbered with ownership and licensing issues.

Use the right most popup menu to chose a background option. You may choose no background, white or black and whether to include the Grid in the output.

Use the save button to execute the save action after all parameter selections are made.

Use the "Add Thumbnail Preview" button to install a custom icon for the exported file. The custom icon will be a small image of the exported drawing or graphics. If this button is not checked the OS X Finder will install an icon in accordance with the system settings and applications available on your system.

The TIFF documentation page provides the foundation documentation for exporting bitmap data files. Review that information for further details concerning file size, image quality and choice of Dots Per Inch (DPI).

We cannot regenerate an EazyDraw vector representation from a PNG export file. If your final work needs to be PNG (or any other bitmap format) be sure to Save and archive the EazyDraw original in case modifications to the original work are needed in the future. You can always generate a revised PNG export from the original-but the reverse is not possible.

Compression is lossless and avoids use of the LZW algorithms. The LZW compression algorithms and the GIF file format have become the target of pay-to-implement issues stemming from Compuserve's ownership of the GIF format and licensing of the LZW algorithms.