Tool - Disk Image Converter
Author: Copyright (C) 2014 by CiderPress authors

Disk Image Converter

This handy tool converts disk images from one format to another. In this case the word "format" refers to the image file format (2MG, SDK, etc.) rather than the disk filesystem format (DOS, ProDOS). With this utility you can add and remove 2MG headers, change DOS-order disks to ProDOS-order, convert 5.25" floppies to nibblized formats, and so on. Read more about disk images here.

Start by selecting the image to open. If the sector ordering cannot be determined, or if you have "Confirm disk image format" enabled in Disk Image preferences, you will be prompted to specify it. (You will also be able to set the filesystem format, but that actually has no effect on the conversion process. If it couldn't be determined, the dialog will show "Generic ProDOS blocks".)

After the image has been opened and examined, you will be asked to select the format of the new image. One or more of the choices may be unavailable depending on the source image format. For example, only 5.25" floppy images can be converted to nibble format, and only 3.5" 800K floppies can be converted to DiskCopy 4.2.

You can also choose to compress the file with gzip. This makes the file smaller and adds a ".gz" extension to the filename. ShrinkIt archives are already compressed, so the gzip flag is ignored. A few emulators and utilities can handle DOS-order images with gzip (.do.gz), but generally speaking you should only add gzip compression if you're planning to store the images rather than use them. The "gzip" checkbox is disabled for images larger than 32MB, because CiderPress doesn't open compressed images larger than that.

Once you have selected the format, click "OK". You will be prompted for the name of the new archive. If you don't specify an extension, the correct one will be added for you. Click "Save" to write the image.

Most disk images are copied as a series of blocks, either ProDOS blocks or pairs of sectors on a 16-sector floppy. If you are copying from a nibble format to a sector format, any unreadable blocks will be skipped. A warning dialog will let you know how many had to be skipped over. If you copy from a nibble format to a new image with the same nibble format (e.g. you're just adding or removing a 2MG header), the data is copied as nibble tracks, and any errors or copy protection are left undisturbed. If the format changes, e.g. you're copying from ".nib" to ".nb2" or ".app", it may not be possible to copy the data directly because the formats are incompatible. In such cases the image will be copied as formatted blocks, converting in and out of nibbles as appropriate.

You will be offered the opportunity to open the image in CiderPress to test it. As with all disk images, this only works if the image has a recognizable filesystem.

The recommended image formats are:

5.25" disks: DOS-order .DO, or (if necessary) .NIB

3.5" disks: ProDOS-order .PO or .2MG

anything else: ProDOS-order .PO or .2MG

These will work with the broadest set of emulators and utilities. Disk images that are 2GB or larger must be stored in .PO format.

Nibble and 2MG formats can store a volume number that DOS uses. CiderPress takes care to preserve this value when converting between formats.

Comments in 2MG files are currently lost when images are converted. This may be fixed in a future version of CiderPress.