Can we improve screenshot DPI

On 24/08/2017 10:02, Whisky-dave wrote:
On Wednesday, 23 August 2017 18:49:25 UTC+1, David B. wrote:
On 23/08/2017 15:39, Savageduck wrote:
[....]
Your question should be; When will I remember to have my iPhone correctly
oriented when shooting video?

I didn't forget ....... I didn't *KNOW*!!!

Thanks for the pointer, Savageduck.

https://www.youtube.com/watch?v=Bt9zSfinwFA

That was great fun, Dave. :-)

Thanks for posting.

I've downloaded an 'App' from the App store called 'Slimmer'. I'll
experiment with it later.

--
Regards,
David B.

A wave from Dustin too! ;-) http://imgur.com/a/5pb8b

On Wed, 23 Aug 2017 14:12:49 +0000 (UTC), Bram van den Heuvel
wrote:

Given news wrote:

He wants better screenshots. Isn't that
enough reason? The problem seems to be
that he doesn't understand that he's not
taking a picture of something, but is rather
just copying the pixels displayed onscreen.

I appreciate that you're helpful since some of the others don't even seem
to understand the question where they think printing is involved or where
they think it matters what you're screenshotting.

The question is just one of what determines resolution of any given
screenshot.

Specifically, how do I increase the number of pixels copied off the screen?

Someone asked "what" I'm taking a screenshot of, where I can't imagine that
his question has any technical merit since it shouldn't matter what you're
taking a screenshot of since the screen is displaying it - so you can't do
better than the screen, right?

Someone else also mentioned printing, which again has no bearing on the
question since the question is only about how to increase the resolution of
the captured screenshot.

Let's say I have a current screenshot resolution of X.
And let's say I want to double that resolution to 2X.

How can a person do that?

They're not going to double their resolution by what they're looking at.
They're not going to double their resolution by printing it.

How can you double the resolution of a screenshot?

Do you change a software driver?
Do you double your screen size?
Do you double your memory?

What determines the resolution of any given screenshot on your own screen?

My ageing laptop screen is 1280 x 800. If I take a screenshot of the
full screen it will give me a jpg of 1280 x 800 pixels. If I take a
screenshot from my other computer I get more because it has a finer
resolution screen, eg 1600x1200.

What gets written into the DPI field of the EXIF info depends on what
software was used to take the screenshot and bears no/little
relationship to that actual pixel size. For instance the software I
use to take screenshots just puts 96DPI into the EXIF, regardless
though for my screen it isn't actually that far off. (13.25" x 8.5"
approx).

If you get a magnfying glass or magnifying software you can see the
individual pixels on the screen and count them up. Unless you then
upsize your image (which means creating pixels that weren't already
there) or downsize (which means condensing the pixels that are there)
you cannot change the screen print resolution because it is fixed by
the screen you have.

--
AnthonyL

"AnthonyL" wrote

| What determines the resolution of any given screenshot on your own
screen?
|
| My ageing laptop screen is 1280 x 800. If I take a screenshot of the
| full screen it will give me a jpg of 1280 x 800 pixels. If I take a
| screenshot from my other computer I get more because it has a finer
| resolution screen, eg 1600x1200.
|

There's a confusion of terminology here. Resolution is
the level of detail. The bigger screen is nice because
you can fit more things onto it. But the degree of detail
of those things is the same.

An icon 32x32 or 128x128.... a program window
600x600px.... a Desktop background photo of your dog
Spot that's 800x600.... None of those things will change.
Those measurements are all in pixels. They'll just look
smaller on the bigger screen. (Unless you set the
background photo to stretch. Then that will get bigger.
But the resolution will not change because it's still an
800x600 image.)

| What gets written into the DPI field of the EXIF info depends on what
| software was used to take the screenshot and bears no/little
| relationship to that actual pixel size.

Bears *no* relationship to pixels, which don't have
a size. It helps here to understand what the picture
actually is, as I detailed somewhat above. The image
is essentially a bitmap. A grid of pixel values stored as
byte data. 3 bytes to a pixel in most cases.

00 00 00 represents a black pixel.
FF FF FF represents a white pixel.
FF 00 00 represents red or blue, depending on how you
read it.

If the first 9 bytes in the bitmap are
FF 00 FF FF 00 FF FF 00 FF
then the first 3 pixels in the image are all purple. That's
it. That's the digital image data. Very simple at that level.
But that's all there is.
The resolution, or level of detail, is already set. How it
gets seen will depend on the monitor, screen size, OS,
your eyesight, room lighting, and even your mood. (As
Jim Morrison said, faces look ugly when you're alone.)
If you're color-blind you may not see purple as others do.

That may seem like irrelevant nitpicking, but when it comes
to graphics those are very real factors. The pixel data in
the image file only represents intensities of red, green
and blue light. Even the structure of our eyes restricts
how we see those colors. (The reason it's so hard to get
a pure yellow is because we don't have cones for yellow.
We see yellow when red and green blend, so most yellows
tend to skew toward orange or lemon. And as interior
decorators know, an off-white is defined in part by what
it's next to.)

Your background photo of Spot will probably have lots
of white and black pixels. Maybe lots of green ones, too,
if he was photographed on a lawn. Those don't have a
size. The only size for the image is the width and height,
pixel count. The image size will depend on the rendering
medium.

If you want more detail then it's not going to happen by
putting the image on computer #2. You're just enlarging
the display of the image. What you can do is to edit the
image in a graphic editor. By doing that you *might* be
able to get a bigger image that still looks good. But you
still won't increase the *resolution* of the original image.

"GS" wrote

| screen shots are just pixels. if you set your display to a higher
| resolution, you get more pixels in the screen shot. that's all.
|
| Now that's *exactly* what I said!!!

I think there's just a mixup of terms here. Nospam
is pointing out the fact that there's no absolute size
in a screenshot -- only pixel dimensions. You're
referring to screen DPI, which most people are unaware
of and which adds an unnecessary complication in
this context. (It's relevant to you writing software, but
it's not relevant to a computer user in practice.)

I don't understand why DPI is even a possible
EXIF tag. It makes no sense. (That reminds me of
Joan Baez singing, "a couple of lightyears ago", not
understanding that a lightyear is distance and not
time.

Steven Roman, in his VB Win32 API Programming
book, includes a dizzying discussion of the difficulty
in even translating between logical screen inches
and pixels.
Windows knows the screen size in pixels, but it can't
know the precise physical size of the screen. With
standard 96 PPI setting, a monitor inch is 96 pixels.
But set it to 120 and a monitor inch is 120 pixels. So
the theoretical physical size of the screen is changed.
Since the display is in pixels, there's no absolute size
and no true PPI, just as with raster images.

In article , Wolf K
wrote:

There's another problem.

When oriented horizontally, with lens to the right or to the left. One
may produce an upside down video when played back on a computer/TV.
There seems to be no consistency. Same problem with horizontal photos.

there is no problem

I didn't say there _is_ one, I said there _may be_ one.

the possibility is so incredibly low that it can be considered to be
zero.

because of the orientation tag in the photo or
video.

Aha! Therefore, a camera without an orientation sensor can't add an
orientation tag. So that must be the problem when the image/video is
incorrectly oriented on playback.

smartphones have orientation sensors, as do all but the ****tiest
cameras, so that situation is *very* rare.

if you're seeing it upside-down, then your software is ignoring the tag
which means your software is at fault.

Nonsense.

not nonsense at all. only ****ty software ignores orientation tags.

"Wolf K" wrote
|
| DPI is not PPI. Eg, my screen is 1920x1080 _pixels_, 21.75" horizontal,
| or 80 PPI. A screen capture with the snipping tool shows shows 120 DPI.
|

See my last post to Garry. It's confusing. The screen capture
tool is probably showing "logical pixels per inch horizontally", as
retrieved from Windows. It's a relative value. As you noted,
that has little to do with the actual screen size, or with inches.
The value in EXIF tags is pointless. People need to stop talking
about DPI outside of printing, and PPI is of no practical use.

In article , Mayayana
wrote:

|
| DPI is not PPI. Eg, my screen is 1920x1080 _pixels_, 21.75" horizontal,
| or 80 PPI. A screen capture with the snipping tool shows shows 120 DPI.
|

See my last post to Garry. It's confusing. The screen capture
tool is probably showing "logical pixels per inch horizontally", as
retrieved from Windows. It's a relative value. As you noted,
that has little to do with the actual screen size, or with inches.
The value in EXIF tags is pointless. People need to stop talking
about DPI outside of printing,

so far so good..

and PPI is of no practical use.

that is absolutely wrong.

Wolf K wrote:
On 2017-08-23 17:59, nospam wrote:

if you're seeing it upside-down, then your software is ignoring the tag
which means your software is at fault.

Nonsense.

Actually, there is one specific failure case, and it's
associated with Apple.

Apple stored metadata in the file header, indicating
orientation. On an Apple box, the displayed result
may be correct. But the scheme doesn't seem to be portable,
and if an Apple user sends the video to a recipient on
a different platform, the video could be upside-down.

For me at least, the way to deal with hillbilly formats,
is to convert them to something that doesn't have
orientation metadata. And the only possible outcome
is What You See (in your video editor) is What You Get
(on the recipient computer when they open your movie attachment).

https://discussions.apple.com/thread...art=0&tstart=0

"only a subset of them actually interpret the EXIF Orientation flag"

Now, think about it. It's one thing to have "in-band" metadata,
a flag defined in a movie or picture format for this specific purpose.
Placing a "hint" in the form of EXIF, is to coin
a phrase, "weak". You can imagine how this would be a
recipe for "platform-specific disaster". EXIF should be
considered "volatile" and "not part of the video or image",
and "can be erased at any time or moment, or even ignored".
For example, some people filter their content with
"EXIF Eraser" to make sure there is no personally identifiable
info, such as GPS coords, in the file header.

That's why doing such a thing in EXIF, is so... "weak".

Paul

In article , Paul
wrote:

if you're seeing it upside-down, then your software is ignoring the tag
which means your software is at fault.

Nonsense.

Actually, there is one specific failure case, and it's
associated with Apple.

nope.

apple, as do other smartphone vendors, writes a proper orientation tag.

apple, adobe and other software vendors check the tag and do the right
thing.

unfortunately, not everyone. any app that ignores the tag is at fault.

Apple stored metadata in the file header, indicating
orientation. On an Apple box, the displayed result
may be correct. But the scheme doesn't seem to be portable,

it's very portable. the tag is standard.

and if an Apple user sends the video to a recipient on
a different platform, the video could be upside-down.

it has nothing to do with apple. lots of cameras write orientation tags.

For me at least, the way to deal with hillbilly formats,
is to convert them to something that doesn't have
orientation metadata. And the only possible outcome
is What You See (in your video editor) is What You Get
(on the recipient computer when they open your movie attachment).

that's very bad and causes problems for those who use software that
checks for the tag.

https://discussions.apple.com/thread...art=0&tstart=0

"only a subset of them actually interpret the EXIF Orientation flag"

software that use the orientation tag is broken. contact the developer
and tell them to fix it.

those who create photos or videos should not cater to those who choose
to use ****ty software.

note that your link says that apple and adobe software works properly.

Now, think about it. It's one thing to have "in-band" metadata,
a flag defined in a movie or picture format for this specific purpose.
Placing a "hint" in the form of EXIF, is to coin
a phrase, "weak". You can imagine how this would be a
recipe for "platform-specific disaster". EXIF should be
considered "volatile" and "not part of the video or image",
and "can be erased at any time or moment, or even ignored".
For example, some people filter their content with
"EXIF Eraser" to make sure there is no personally identifiable
info, such as GPS coords, in the file header.

it's possible to remove gps while leaving the orientation tag.

in other words, user error.

That's why doing such a thing in EXIF, is so... "weak".

it's not weak and is standard across the industry.

Windows knows the screen size in pixels, but it can't
know the precise physical size of the screen. With
standard 96 PPI setting, a monitor inch is 96 pixels.
But set it to 120 and a monitor inch is 120 pixels. So
the theoretical physical size of the screen is changed.
Since the display is in pixels, there's no absolute size
and no true PPI, just as with raster images.
A mizup of terms for sure! We can blame Microsoft for that, though...

Windows refers to this as the screen resolution 'DPI Setting' in ControlPanel.
Changing it as described effectively changes what a screenshot captures in
pixels for the specified area (width/height) of the capture. Nothing changes
physically in the captured image so it reflects the exact current DPI setting
of screen resolution at the time of capture. Nor does the screen resolution
change; -just its ppi. So on my 1920x1200 display's DPI Setting of 120,
everything appears smaller than a 96 setting.

Not sure why all these Windows experts don't know about this ControlPanel
setting or its effects on screenshots when changed. Seems really basic to me!

--
Garry

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