PCX Image in Paintbrush Has Different Colors

• Microsoft Windows operating system versions 3.0, 3.0a

SUMMARY

The colors of a PCX image viewed in Windows 3.0's Paintbrush may not match the color of the same PCX image viewed through another application.

MORE INFORMATION

There are several reasons for this discrepancy:

• The PCX graphical file format has no standard. It has gone through numerous changes dating back to the CGA (color graphics adapter). It is impossible to have one viewing program compatible with all these different versions.
• Individual companies implement their own standards in different ways and to different extents.
• Graphical standards are defined through different display adapters. Each display adapter has its own variation of a color palette and palette limitations (for example, number of colors appearing at one time).
• Windows has a graphical user interface (GUI), which is making demands on display adapter memory at the same time the PCX image is. The hardware or display driver may not be able to handle the demand.
• PCX images have a file header that contains a self-defining color table. This information may not transfer correctly.
• Windows has defined and was built-around a new level of graphical format, the device independent bitmap (DIB), which is not directly compatible with PCX. DIBs were designed to get beyond the problems associated with the PCX format.

REFERENCES

"Microsoft Systems Journal," July 1991, pages 85-93.