PNGExtra – Troubleshooting

Troubleshooting problems with PNGExtra

PNGExtra will handle most problems, such as corrupt PNG files, disk errors and so forth. This page lists these common errors plus some of the less obvious problems and their solutions.

Typical Errors

Corrupt or Invalid PNG Files

PNGExtra performs extensive checking that all required sections of a PNG file are intact and valid. When any critical section is missing or invalid, PNGExtra will not process that file.

Non-PNG Files

Some people mistakenly believe that an image in a different image file format – such as a GIF file – can be converted to the PNG file format simply by renaming the file (eg. renaming ABC.GIF to ABC.PNG). However, changing the filename does NOT change the file contents, so the data within the file will not be in the correct PNG format.

As above, PNGExtra will consider such a PNG file to be corrupt because it will almost certainly be missing one or more critical sections. PNGExtra will not try to identify what other type of file it “might be”. Instead, it will simply skip that file.

Truncated PNG Files

A PNG file that has been cut short can easily occur when downloading images from the Internet. For example, pressing the [Esc] key before an image has completely downloaded may create a truncated PNG file. PNGExtra will show a warning and will still try to optimize such a file, but will make no attempt to properly terminate the chopped-off portion.

PNG Files With “Read-Only” Attribute

Windows allows any file to be tagged with a “Read-Only” attribute in order to prevent such files being modified. PNGExtra will respect that attribute and will not attempt to process such a file.

PNG Files From CDs or DVDs

CDs and DVDs normally can't be written to directly without special CD or DVD “Burning” software. This means three things:

  1. PNGExtra does not contain any such “Burning” capabilities, and therefore cannot process PNG files directly on a CD or DVD.
  2. All files on CDs and DVDs (not just PNG files) are automatically given a “Read-Only” attribute, which – as explained above – means that Windows is indicating that the file can not (or should not) be modified. This is a further reason preventing PNGExtra from processing PNG files directly on a CD or DVD.
  3. When files are copied by Windows, the file attributes are normally copied as well. Any PNG files copied from a CD or DVD to a hard drive will thus inherit the Read-Only attributes. Once again, PNGExtra will not be able to process those PNG files.

If files on a CD or DVD need to be processed with PNGExtra, they should firstly be copied to a hard drive, then the Read-Only attributes need to be reset. Consult the Windows “Help” for details on how to clear the read-only attributes of any such files.

Disk Space Errors

It's possible to run out of disk space whilst optimizing, especially if the option: • Backup Original Files is selected, as some disk space will be consumed for every single PNG file that is optimized.

If this happens when processing an individual file, PNGExtra will simply show a disk space error and stop. If it happens while processing a whole library of files, PNGExtra will quit processing the current file but will nonetheless attempt to keep running, the theory being that enough disk space may still be available to optimize some of the remaining smaller PNG files.

Errors During Batch Processing

PNGExtra's greatest strength is that it is designed to run over a whole library of PNG files, often called “Batch Processing”. In order to find out about any errors without having to pause for each and every one, do the following:

  • Un-check the error option: • Pause on Errors;
  • Check the log file option: • All Files Processed.

If PNGExtra does find any errors, processing will proceed without stopping. Once completed, examine the log file for a brief description of any errors found.