Open CDR File

Compression and Size management in CDR files

CorelDRAW, the software which creates files with CDR extension, uses a compression library called ZLIB, which uses DEFLATE compression algorithm and was originally implemented by Jean-loup Gailly and Mark Adler. DEFLATE algorithm is a variation of LZ77 (Lempel-Ziv 1977) compression algorithm.

One of DEFLATE algorithm main advantages is that no information is lost in the compression process. Unlike lossy compression algorithms and systems, DEFLATE is able to decompress the data in exactly the same state it was prior to compression.

CorelDRAW incorporates an implementation of the ZLIB algorithm in its files, so its files are already compressed. This option can be disabled, giving the program more speed to open and save documents, but it will produce significantly larger files.

Compressing a CDR file which was saved with “Enabled compression” option will not produce a smaller file, since it is already compressed by default; in fact, a ZIP or RAR compressed file may be even larger than the original CDR itself. The advantage of using ZIP, RAR, etc., is the option of segmenting a large CorelDRAW file into several smaller files which may be useful when transferring the file. It should be added that compression with ZIP or RAR do not cause loss of information, although if the compressed file is damaged it can no longer be decompressed.

Undo history

Each time you execute a command in CorelDRAW, the information is saved, to allow Undo (ctrl + z) but also to allow Redo (Ctrl + May + Z). CorelDRAW keep a history list of the commands executed, allowing you to return to any point on that list, without having to do Ctrl + Z ten times in a row.

If in CorelDRAW it is possible to have 99 levels of Undo (could be changed in Tools->Options->General menu). It means that each open CDR file will generate up to 99 edit snapshots in memory. Even on powerful computers, a simple 10-megabyte file could collapse the system due to the size of Undo history.

Size management Recommendations

A good tip is to reduce the Undo list size to a lower number which makes it useful but keeps it reasonable in size. Save CorelDraw document frequently, do not spend hours without saving anything. If it takes too long to save, deactivate compression and it will do so much faster. If test changes are to be made, and you do not want to lose the previous edits copy, it is preferable to "Save as..." under another file name.

If the file is very large split it into multiple parts which could be edited separately. Disable unused options and do not add features that you don’t critically need until the final edits.