Working with Images

Wed Feb 6 11:10:36 PST 2008

Rick...

You are very correct about my brashness. My apologies to all of you. 
I was anxious to try and squelch some misconceptions and got carried 
away. David Creamer was particularly incensed with me because he 
thought I was aiming the whole rant at him. This was not the case, of 
course, but I can see his point. in the meantime, he and I have 
called a truce, as we both have better things to do.

Dude...
******************************************
At 06:26 AM 2/6/2008, richard.melanson at us.tel.com wrote:
>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-bounces at 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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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