Visio Insights
The official blog of the Microsoft Visio product team

How Far Can I Zoom In?

How Far Can I Zoom In?

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Here’s a recent question on the newsgroups that has come up several times in the past.  It seems that the larger you make a page in Visio, the less you can zoom in to see the details.  This is true.  There is a maximum zoom limit in Visio, and this maximum depends on the size of your page.

 

The limitation on zoom is tied to the way Visio uses Windows’ GDI display component to render pages.  A Visio page is one big surface that is clipped to fit in the drawing window.  This allows capabilities such as smooth panning / scrolling and rapid zoom changes because the rendered image does not need to be constantly reconstructed.  In Windows 9x systems this display surface was limited to a maximum size of 32767 x 32767 pixels - basically a 16-bit system limitation.

 

To calculate the maximum zoom level, Visio uses this basic formula:

Max Zoom = (32767 / (Page size in inches * Screen pixels per inch)) * 100%

Take an example drawing with the largest page dimension equal to 34 inches and a standard monitor pixel density of 96 DPI.  This formula evaluates to 1004%.  If the page size increases, the maximum zoom decreases proportionally.

 

More recent versions of Windows support larger ranges in GDI.  Starting with the latest service pack of Visio 2003, we have updated our zoom logic to take advantage of this headroom.  At a minimum, you can zoom into your drawing at 1000% regardless of page size.  The formula above is still used to determine the maximum zoom.  Thus the zoom limit is the larger of the formula result or 1000%.

 

Hopefully this addresses most of the situations where zooming was restricted with large pages.

 

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