export with "bmp" format with standard DPI headers

**rpc9943** · 31 May 2011, 04:47 PM

This is quite specific because my employment is using software that is specialized for use with BMP's. I am not sure why we do not have the option to set the DPI header upon export. Every other software I have used includes this.

Thank you
RonC

**Soquili** · 31 May 2011, 04:54 PM

Ron can you attach a screen shot of any software's option to set a bmp dpi header?

I don't recall ever seeing one.

Microsoft bitmap images (.bmp) has always been a default of 96 dpi (standard windows resolution).

**Soquili** · 31 May 2011, 05:03 PM

This link shows the Windows bitmap file structure. http://www.fileformat.info/format/bm...86d9c/view.htm

The header specification does not include any dpi information that I can find.

**Soquili** · 31 May 2011, 05:10 PM

Maybe you are referring to a .dib (device independant bitmap)? File structure: http://www.fileformat.info/format/bm...c67a4/view.htm

The .dib still image format contains an embedded jpeg image which does support a dpi.

**Soquili** · 31 May 2011, 05:39 PM

It appears there is a resolution for Target Device in the BITMAPINFOHEADER structure.

The values are normally set to zero although it is possible to set the number of pixels per meter that the target device supports.

The biXPelsPerMeter is used for Horizotal resolution and biYPelsPerMeter for the Vertical resolution. Both refer to a specific target device resolution. An application can use those values to determine a specific bitmap within a resource group to send to a specific target device.

The display screen is usually the target device for a .bmp image so the biXPelsPerMeter and biYPelsPerMeter are set to 0 by current applications creating an individual bitmap image for display.

I'm not aware of applications that are created to support output devices that work using Pixels Per Meter, although it sounds like a good feature for (extremely) large format printers designed for billboards.

**rpc9943** · 31 May 2011, 05:59 PM

I can define further what I mean once I talk to my boss, he codes the software for this so he's pretty familiar with the .bmp file...

**GerryI** · 31 May 2011, 10:44 PM

Don't worry, we know all about the PelsPerMeter settings. The value equivalent to 96dpi is 3780 (actually 3779.53). Writing different values into these fields in a BMP used to (i.e. more than 10 years ago) cause many more problems than it solved but we should probably look at it again.

Gerry

**Soquili** · 01 June 2011, 01:45 AM

Thanks Gerry, I wasn't worried.

If the issue of setting values other than zero in those fields were resolved I think it would have been significant enough to have been heard around the world.