Wallpaper bitmap CPU usage?

[Ed Warner]

Does anyone know how memory is allocated for Windows full-screen
wallpaper backgrounds?

As an example, if your screen resolution is 1024x768 and you "Stretch"
(technically shrink) a 2048x1536 photo to fit the screen, will it use
roughly twice the RAM as it would if you resampled it to 1024x768
beforehand? Something tells me it's more complex than that.

These *.bmp wallpaper files are quite large and I don't know if Windows
puts the entire image in RAM or only the pixels needed to fill your
screen dimensions. I notice that Windows keeps the original image
dimensions stored in the *.bmp file "behind the scenes." Are you
wasting memory if you don't resample/downsize the image first?

Do small tiled patterns use significantly less RAM than full-screen
photos? Lastly, is there a specific "Process" in Task Manager that
shows resources used to display wallpaper? Thanks for any info.

Ed




P.S. If you see it, please ignore an earlier version of this post that
I cancelled to fix a typo.

 

[Jim]

Does anyone know how memory is allocated for Windows full-screen
wallpaper backgrounds?

As an example, if your screen resolution is 1024x768 and you "Stretch"
(technically shrink) a 2048x1536 photo to fit the screen, will it use
roughly twice the RAM as it would if you resampled it to 1024x768
beforehand? Something tells me it's more complex than that.

A 2048x1536 photo has the same number of pixels regardless of the size of
the window. However, 2048x1536 is four times as many pixels as 1024x768.
What might happen is that the graphics adapter throws away every other
pixel... And, this all happens inside the computer memory; the file itself
is not changed.

If you should decide to do the downsizing before hand, all you have done is
change the internal representation of the image. Until you save the memory
to disk, the original file is not changed.
Jim

 

[Ed Warner]

A 2048x1536 photo has the same number of pixels regardless of the size of
the window. However, 2048x1536 is four times as many pixels as 1024x768.
What might happen is that the graphics adapter throws away every other
pixel... And, this all happens inside the computer memory; the file itself
is not changed.

But RAM is my only concern, so is system memory taxed according to
filesize, or just the screen area? I am looking for a technical
explanation or a Windows process that shows wallpaper RAM usage.

If you should decide to do the downsizing before hand, all you have done is
change the internal representation of the image. Until you save the memory
to disk, the original file is not changed.
Jim

The full original dimensions are indeed saved to disk as a special
*.bmp file. In testing a particular image, the size ends up being 9 MB
at 2048x1536 and 2.3 MB at 1024x768. For a 5-megapixel image
(2560x1920) it was 14 MB. The XP file location is C:\Documents and
Settings\<username>\Application Data\Microsoft\ (using standard Windows
wallpaper method).

So, every time Windows boots it would appear to be loading all those
megabytes if you only "stretch" the image. Definitely not so?

Ed