About GDI
Introduction
Following up on the previous article, this time we will cover GDI as a topic related to SVF. In SVF, GDI technology is utilized for form rendering on Windows and for print processing via drivers.
What is GDI?
GDI (Graphics Device Interface) is a rendering technology adopted since the early days of Windows, which enables line drawing, filling, bitmap manipulation, and font rendering through APIs. Since Windows XP, GDI+ has been introduced to support anti-aliasing, transparency, and gradient rendering, adding more advanced graphic features.
GDI and GDI+ are rendering specifications provided by Microsoft, with APIs available for C/C++ and the .NET
Framework. By using these, you can access screen and printer device drivers to execute rendering.
For detailed specifications, please refer to the following links.
・GDI Specifications
・GDI+ Specifications
About EMF
In explaining GDI, we will also touch upon EMF (Enhanced Metafile Format). EMF is one of the image file formats for Windows and is a vector-based file that describes GDI APIs. This format is also used as an intermediate data format for rendering and as a spool file format for printers (a format for temporarily saving print data), enabling efficient print data processing.
As the name suggests, EMF is an "enhanced metafile," which has been strengthened based on WMF (Windows Metafile Format). Also, similar to GDI+ for GDI, there is a format called EMF+ with further extended rendering capabilities. EMF+ supports GDI+ rendering commands and can reproduce rendering content with high precision.
The specifications for EMF and EMF+ are also published by Microsoft. For detailed specifications, please refer to the following links.
・EMF Specifications
・EMF+ Specifications
The evolution and relationships of the file formats are summarized as follows.
About EMF in SVF
EMF plays an important role in the printing functions of SVF in Windows environments. The main function of SVF is to convert form data directly into PDL (Page Description Language) and process it as a printer driver. However, by converting forms into the EMF format that Windows can understand, it becomes possible to render efficiently on both printers and screen displays.
If you are printing a form to only a specific printer, you can print at high speed by selecting the PDL for that printer. On the other hand, if you want to print to multiple manufacturers' printers after previewing the form on Windows, you can achieve efficient print processing by outputting to the EMF format first and then printing via the printer driver after the preview.
SVF has EMF models and EMFPLUS models, which correspond to Windows EMF and EMF+ respectively. However, these are not completely standard Windows formats, and some proprietary specifications are adopted. For example, while the Windows EMF specification corresponds to one file per page, SVF realizes a format that manages multi-page forms in a single file through its own extensions.
Summary
GDI and EMF are core technologies in Windows rendering and print processing, and even with the emergence of the latest technologies, they are still widely used today due to their high reliability and compatibility. SVF utilizes these technologies to streamline rendering and print processing on the Windows platform.
SVF is mainly used for printing forms on printers, but it has the flexibility to output forms in various formats such as EMF, SVG introduced last time, and PDF. By selecting the optimal format according to the application, efficient form processing is realized in various business scenarios.
We hope that SVF can contribute to the efficiency of your business.
