Dude, you may be the expert on this, and the info you supplied in your response 
is so good I am saving it, but how about a little respect for everyone on the 
list. I believe whatever anyone said in an attempt to help they believed to be 
accurate and helpful. To say and I quote you "Well, I've had enough of this 
nonsensical babble. None of you seem to understand what you are talking about 
when it" is a little strong. Life is too short, take a deep breath and enjoy!!
Rick

-----Original Message-----
From: framers-bounces at lists.frameusers.com 
[mailto:framers-boun...@lists.frameusers.com] On Behalf Of Dennis Brunnenmeyer
Sent: Tuesday, February 05, 2008 2:37 PM
To: David Creamer; framers at lists.frameusers.com
Subject: RE: Working with Images

Rant begins...

Well, I've had enough of this nonsensical babble. None of you seem to 
understand what you are talking about when it comes to dealing with screenshots 
and raster images, (a.k.a. bitmapped images) as opposed to vector or llne art.

First of all, display devices, whether printers or monitors, have an upper 
limit on their ability to resolve (print or display) image detail, which by the 
way is what "resolution" is a measure of...meaningful detail. The best my aging 
but faithful laser printer can do is 600 dpi, while my uppity LCD monitor can 
display up to 100 dpi, with its1600 x 1200 native resolution on an LCD panel 
that is exactly 16" wide x 12" tall."  You cannot see nor capture anything and 
create a screenshot image with higher resolution than the display device. You 
cannot print anything with higher resolution than the printer can resolve. If 
you feed a high resolution image to a medium resolution printer, it will 
interpolate (resample) the image down to medium resolution quality. It has to, 
as it cannot put all of that information on paper. If you take an very high 
resolution (total pixel count) image of size 4000 x 3000 pixels (12 megapixels) 
and display the full image it on a monitor like mine, you will
not see all of detail in the image and hence you will not be able to capture 
all of the detail in a screenshot.

Most of you seem to appreciate this, but some of you think you can improve 
resolution by artificial means. No, you cannot.

A true measure of the resolution of an image is the original size of the image 
in total pixels, assuming it is true to begin with. That is, assuming a perfect 
digital camera with a perfect lens and the ability to produce a "raw" bitmap 
(rather than a compressed JPEG file), that 12 megapixel CCD image sensor will 
produce a significant improvement in the resulting image over a 2 megapixel CCD 
sensor. 
That image quality is NOT described by either ppi or dpi. It is a function of 
the number of pixels in the X direction and the number of pixels in the Y 
direction.

Now the plot thickens when I return to the subject of screenshots, because if I 
run my graphics card at 1600 x 1200, the type, icons and dialog boxes are 
uncomfortably small for me to read on the monitor, so I set the graphics card 
to display its images at 1280 x 960 dpi. 
At this point, the maximum image size that can be displayed without loss of 
resolution is now 80 ppi. That's 1280 divided by 16. 
[Unfortunately, since the graphics card's resolution doesn't match the native 
resolution of the LCD panel, the on-screen picture is not as crisp as it could 
be. This is a result of "aliasing" artifacts, but that's a topic for a 
different thread.]

Note that in the above paragraph, I switched from dpi for display devices to 
ppi when describing image size. This is a meature of the physical size of a 
digital image (as printed or displayed) and should be described in ppi. The 
ability of a device to display or print an image should be described in dpi, or 
alternatively, lpi for lines per inch, or pixel spacing, as in 0.25mm. There is 
a tendency to intermix this terminology and hence confuse the issues you are 
discussing.

Now that I have set my graphics card to 1280 x 960 for this monitor, the 
maximum resolution of any image I capture from the screen is 80 ppi, regardless 
of whether I capture a whole screen or just a region of it. If I set the 
"resolution" of the screen capture program (Snag-It or HyperSnap) to 80 ppi, 
then the resulting image will be the same physical size as it appeared on the 
screen, 100%. If I set the capture "resolution" to 160 ppi, then the image will 
be half the physical size as it appeared on the screen, BUT IT WILL HAVE 
EXACTLY THE SAME NUMBER OF PIXELS. The resolution has not be improved, as no 
more detail has been added.

Upsampling and/or downsampling using any kind of pixel resampling (a.k.a. 
interpolation), whether bicubic or otherwise, ALWAYS removes detail from the 
image. In either case, new pixels are created that are some kind of average of 
the original ones. They're guesses at what shoud be there at that point in the 
image, and not real information that wasn't there before. No new detail nor 
image improvement can be added by interpolation.

Now, however, you can re-scale an image in programs like Photoshop by keeping 
the same number of pixels (do not interpolate) and altering the size of the 
image in the X and Y directions equally. For example, if I took the 160 ppi 
screenshot described in the previous paragraph and re-scaled it in Photoshop 
without  resampling the image, and if I prescribed a new size of 80 ppi, the 
resulting image would grow back to 100% in size and have still have exactly the 
same number of pixels as before. The resolving power of the image has not 
changed, and no more detail has been provided. This is a correct way to get an 
image to the size you want it in your document. Another way is to import it as 
is and resize it in Frame using the image's corner anchor points while holding 
the Shift key down.

Don't mislead yourselves and others by thinking that the more "resolution" in 
your screenshot capture application you use gives you better results, and don't 
mislead yourselves by thinking you can add more resolution by upsampling (or 
rescaling, for that matter) to a different ppi or by adding more artificial 
pixels.

Now, on another topic, there seems to be a rule of thumb that "most SVGA 
screens are 96dpi." Someone came up with the statement that a 20" screen with a 
1280 x 1024 display is, of course, 96 dpi. That's utter nonsense. Given that 
screen size is measured on the diagonal, and assuming the old standard 4:3 
aspect ratio, a 20" screen is 16" 
wide and 12" tall...rather like my Samsung LCDs. With 1280 pixels in the X 
(horizontal) direction, the screen resolution is 80 dpi, not 96 dpi. Any way 
you manipulate the numbers, 96 dpi is not a result. By the way, here I assumed 
a 4:3 aspect ratio, which is the ratio of width to height. If I ran my graphics 
card at 1280 x 1024, circles would be egg-shaped, since that resolution calls 
for a screen with a
5:4 aspect ratio. Of course, wide screens have a different aspect ratio, but 
the principles are exactly the same.

I have no idea what David meant by this statement:  "Again, referring to my 
last post, monitor resolution only counts if capturing an entire screen." 
Monitor size DOES count if you're trying to calculate the resolving power of 
your monitor in dpi and hence the maximum resolution attainable in a 
screenshot. It's the horizontal resolution of your graphics card setting 
divided by the width of the display area in inches or centimeters, or in the 
example given,
1280/16 = 80 dpi.

End of rant ...

Flame away...but be sure you know what you are talking about and quit 
misleading others if you don't understand this.

Dennis Brunnenmeyer
***************************************************************************************


At 09:09 AM 2/5/2008, David Creamer wrote:
> > How can SnagIt capture an image at a higher resolution than what the 
> > screen is set to?  A 20" screen at 1280 x 1024, for example, is 96
> DPI.  How do you
> > get 200 DPI out of that?
>
>Screen size (20") is meaningless, only the monitor resolution counts.
>Again, referring to my last post, monitor resolution only counts if 
>capturing an entire screen.

Dennis Brunnenmeyer
Director of Engineering
CEDAR RIDGE SYSTEMS
15019 Rattlesnake Road
Grass Valley, CA 95945-8710
Office: (530) 477-9015
Fax:  (530) 477-9085
Mobile: (530) 320-9025
eMail:  dennisb /at/ chronometrics /dot/ com 
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