OpenEuphoria

1. JPEG Resolution

• Posted by Alex Chamberlain <alex.chamberlain at tiscali.co.uk> Mar 11, 2006
• 520 views
• Last edited Mar 12, 2006

Hi,

Can anyone help me by providing a function to tell me the resolution of a JPEG
File?

I'm using GD at the moment.

Thanks,

Alex

3. Re: JPEG Resolution

• Posted by Alex Chamberlain <alex.chamberlain at tiscali.co.uk> Mar 12, 2006
• 522 views

Al Getz wrote:
> 
> Alex Chamberlain wrote:
> > 
> > Hi,
> > 
> > Can anyone help me by providing a function to tell me the resolution of a
> > JPEG
> > File?
> > 
> > I'm using GD at the moment.
> > 
> > Thanks,
> > 
> > Alex
> 
> Hi there,
> 
> 
> Are you talking about the DPI (dots per inch) ?
> 
> 
> Al

Yeah!

5. Re: JPEG Resolution

• Posted by Brian Broker <brian_broker at yahoo.com> Mar 13, 2006
• 525 views
• Last edited Mar 14, 2006

Al Getz wrote:
> 
> Alex Chamberlain wrote:
> > 
> > Al Getz wrote:
> > > 
> > > Alex Chamberlain wrote:
> > > > 
> > > > Hi,
> > > > 
> > > > Can anyone help me by providing a function to tell me the resolution of
> > > > a JPEG
> > > > File?
> > > > 
> > > > I'm using GD at the moment.
> > > > 
> > > > Thanks,
> > > > 
> > > > Alex
> > > 
> > > Hi there,
> > > 
> > > 
> > > Are you talking about the DPI (dots per inch) ?
> > > 
> > > 
> > > Al
> > 
> > Yeah!
> 
> 
> Hi again Alex,
> 
> 
> Sorry, i have an inch thick stack of notes on the jpg file format
> and i cant seem to find anything on the dpi of the file.  It's 
> been so long now since i've worked with this i dont remember how
> to find or calculate this.  Maybe ask again or on another
> forum?
> 
> 
> Al
> 
> 
> My bumper sticker: "I brake for LED's"

Correct me if I'm wrong but isn't DPI a measurement of an output device?

How big is a pixel?
http://heim.ifi.uio.no/~gisle/photo/pixels.html

-- Brian

7. Re: JPEG Resolution

• Posted by Brian Broker <brian_broker at yahoo.com> Mar 14, 2006
• 514 views

Al Getz wrote:
> 
> Brian Broker wrote:
> > 
> > Al Getz wrote:
> > > 
> > > Alex Chamberlain wrote:
> > > > 
> > > > Al Getz wrote:
> > > > > 
> > > > > Alex Chamberlain wrote:
> > > > > > 
> > > > > > Hi,
> > > > > > 
> > > > > > Can anyone help me by providing a function to tell me the resolution
> > > > > > of
> > a JPEG</font></i>
> > > > > > File?
> > > > > > 
> > > > > > I'm using GD at the moment.
> > > > > > 
> > > > > > Thanks,
> > > > > > 
> > > > > > Alex
> > > > > 
> > > > > Hi there,
> > > > > 
> > > > > 
> > > > > Are you talking about the DPI (dots per inch) ?
> > > > > 
> > > > > 
> > > > > Al
> > > > 
> > > > Yeah!
> > > 
> > > 
> > > Hi again Alex,
> > > 
> > > 
> > > Sorry, i have an inch thick stack of notes on the jpg file format
> > > and i cant seem to find anything on the dpi of the file.  It's 
> > > been so long now since i've worked with this i dont remember how
> > > to find or calculate this.  Maybe ask again or on another
> > > forum?
> > > 
> > > 
> > > Al
> > > 
> > > 
> > > My bumper sticker: "I brake for LED's"
> > 
> > Correct me if I'm wrong but isn't DPI a measurement of an output device?
> > 
> > How big is a pixel?
> > <a
> > href="http://heim.ifi.uio.no/~gisle/photo/pixels.html">http://heim.ifi.uio.no/~gisle/photo/pixels.html</a>
> > 
> > -- Brian
> 
> Hi Brian,
> 
> 
> What i was assuming was that he was after something like the bitmap
> file header contains: PelsPerMeter for Vertical and Horizontal,
> but couldnt find anything that had a unit of length in it.
> It's possible to calculate (for jpg) but i cant seem to find the doc's on it.
> I think it's because when i was doing my jpg decoder i had no use
> for the resolution data because most of the time there's only one picture
> to choose from and one monitor to choose from.
> I think the last time i worked on my .jpg decoder (in the archives) was
> around 1999 or so.
> 
> 
> Al
> 
> 
> My bumper sticker: "I brake for LED's"

But I wonder how many apps actually use "PelsPerMeter"?  There seem to be few
explanations of what this info is for.  I did find this:

"The PelsPerMeter fields doesn't seem to be particularly important, is often
just set to zero, and is supposed to describe how many pixels are to be displayed
in one meter of space (in case anyone has a monitor a meter wide). This seems to
relate to how the bitmap was intended to be displayed and viewed."

To me, that seems to imply that a viewer app using this information would have
to stretch and/or compress an image to make it fit an intended area.  But still I
wonder how many image viewers or printer drivers actually do this?

-- Brian

9. Re: JPEG Resolution

• Posted by Brian Broker <brian_broker at yahoo.com> Mar 14, 2006
• 510 views

Chris Burch wrote:
> 
> Hi
> 
> Doesn't a graphic file, any graphic, just have a dimension, eg 320 * 240
> pixels,
> loaded into memory from whatever format, manipulated, then output to whatever
> format?
> 
> Chris
> 
> <a
> href="http://members.aol.com/chriscrylex/euphoria.htm">http://members.aol.com/chriscrylex/euphoria.htm</a>
> <a href="http://uboard.proboards32.com/">http://uboard.proboards32.com/</a>
> <a
> href="http://members.aol.com/chriscrylex/EUSQLite/eusql.html">http://members.aol.com/chriscrylex/EUSQLite/eusql.html</a>

Well, that's what I thought but here's some more info that I found interesting. 
Apparently the jpeg format does have a DPI setting that apps might use.

http://www.rdpslides.com/pptfaq/FAQ00075.htm

-- Brian

11. Re: JPEG Resolution

• Posted by Jeremy Peterson <ptl99 at hotmail.com> Mar 14, 2006
• 500 views

Brian Broker wrote:
> Correct me if I'm wrong but isn't DPI a measurement of an output device?
> 
> How big is a pixel?
> <a
> href="http://heim.ifi.uio.no/~gisle/photo/pixels.html">http://heim.ifi.uio.no/~gisle/photo/pixels.html</a>
> 
> -- Brian

DPI means dots per inch, and just measures how many pixels there are in one
cubic inch of the screen.  So when it's 64 by 64 DPI, that means that an inch of
the picture is 64 pixels long and 64 pixels wide.

Jeremy

Edmund Burke: "All that is necessary for evil to triumph is for good men to do
nothing."

13. Re: JPEG Resolution

• Posted by Jeremy Peterson <ptl99 at hotmail.com> Mar 14, 2006
• 525 views
• Last edited Mar 15, 2006

It depends on what resolution you set it at.  If they both have the same
resolution, it would be the latter.

Jeremy

15. Re: JPEG Resolution

• Posted by "Patrick Barnes" <mrtrick at gmail.com> Mar 15, 2006
• 513 views

On 3/15/06, Evan Marshall <guest at rapideuphoria.com> wrote:
> If you have a 64x64 DPI image and a 14" monitor set to 800x600 and a 21"
> monitor set to 800x600, then by your first post, both monitors show the i=
mage
> with identical dimensions (1 *square* inch), but how can that be if the p=
ixels
> are larger on the 21" monitor?

monitor dimensions * DPI = resolution

Thus, a 64x64 DPI image of a given resolution will take up a certain
amount of screen real-estate... often DPI is ignored for a monitor's
display, as DPI is fixed to the screen's resolution.

--
MrTrick
----------

17. Re: JPEG Resolution

• Posted by Alex Chamberlain <alex.chamberlain at tiscali.co.uk> Mar 15, 2006
• 513 views
• Last edited Mar 16, 2006

Hi,

I was only really interested in DPI, as for a decent photo print you need at
least 300dpi.

Alex

19. Re: JPEG Resolution

• Posted by Pete Stoner <stoner.pete at gmail.com> Mar 16, 2006
• 518 views

Al Getz wrote:
> 
> If you want buttons to display the same size on different monitors
> you may wish to draw them using the dpi of the display as one of
> the params too.  If you want the button 1 inch wide on a 96 dpi
> monitor i guess you'd need 96 pixels across, while on a 180 dpi
> monitor you'd need 180 pixels across, so the width param in these
> two cases would be either 96 or 180.

On the subject of correcly sizing for different resolutions, its not so much
wanting buttons to be the same size its more that the same font will be larger at
higher resolutions. This can mean that any text may be too large for its control.
As I wanted my apps to look good regardless of the users resolution setting I
came up with the following code.

without warning
without trace
include win32lib.ew

global constant
  -- for correct window centering on screen (UK spelling of 'centre'!)
 Centre   = "Centre"  
 
constant 
    xPARAMS = 1,
    yPARAMS = 2,
    cxPARAMS = 3,
    cyPARAMS = 4,
    X = 1,
    Y = 2

atom dc
atom cxDpi, cyDpi

dc = getDC ( Screen )
cxDpi=(w32Func(xGetDeviceCaps,{dc,LOGPIXELSX})/96)
cyDpi=(w32Func(xGetDeviceCaps,{dc,LOGPIXELSY})/96)
releaseDC(Screen)

integer centerScreenX, centerScreenY
sequence ScreenSize
ScreenSize = getRect(Screen)
centerScreenX = floor( ScreenSize[3]/2 )
centerScreenY = floor( ScreenSize[4]/2 )

function DI(integer Orientation, object pixels)
    if Orientation = X then
        return floor(pixels * cxDpi)
    elsif Orientation = Y then
        return floor(pixels * cyDpi)
    end if
    end function

global function dpiCreateEx(integer pControl, sequence caption, atom pOwner,
object x, object y, object cx, object cy, object styleFlags, object
            exFlags )
sequence params
sequence IgnoreControls -- controls not needing DPI change
params = {x, y, cx, cy}

IgnoreControls = {Menu, MenuItem}

    if not find(pControl, IgnoreControls) then 
-- if control is a Window then leave position stuff alone
        if pControl != Window then  
       -- chk for relational positioning i.e. ix X < 1 then 
       -- x position must be a 0.x (%) value so leave alone
          if integer(x) and x > 1 then 
            params[xPARAMS] = DI(X, x)
-- also handle w32lib constant calls like 'Center' and {w32AltEdge. -20} 
          elsif sequence(x) and atom(x[2]) and length(x) = 2 then
            params[xPARAMS] = x
            params[xPARAMS][2] = DI(X, x[2])
          end if  
          if integer(y) and y > 1 then 
            params[yPARAMS] = DI(Y, y) 
          elsif sequence(y) and atom(y[2]) and length(y) = 2 then
            params[yPARAMS] = y
            params[yPARAMS][2] = DI(Y, y[2])
          end if
        end if

        if integer(cx) and cx > 1 then 
            params[cxPARAMS] = DI(X, cx) 
        elsif sequence(cx) and atom(cx[2]) and length(cx) = 2 then
            params[cxPARAMS] = cx
            params[cxPARAMS][2] = DI(X, cx[2])
        end if
        if pControl != SortedCombo then         
          if integer(cy) and cy > 1 then 
            params[cyPARAMS] = DI(Y, cy) 
          elsif sequence(cy) and atom(cy[2]) and length(cy) = 2 then
            params[cyPARAMS] = cy
            params[cyPARAMS][2] = DI(Y, cy[2])      
          end if
        else
          params[cyPARAMS] = cy 
        end if
    end if
    
    if pControl = Window then   
-- if control is a 'centered' Window then correctly center it!
if equal(x, Centre) then params[xPARAMS] = centerScreenX - floor(
      params[cxPARAMS]/2 )
       end if
if equal(y, Centre) then params[yPARAMS] = centerScreenY - floor(
      params[cyPARAMS]/2 )
      end if
    end if
        
return createEx( pControl, caption, pOwner, params[xPARAMS],  
   params[yPARAMS],params[cxPARAMS], params[cyPARAMS], styleFlags, exFlags)

    end function

global function dpiCreate(integer pControl, sequence caption, atom pOwner,
            object x, object y, object cx, object cy, object styleFlags )
        
 return dpiCreateEx( pControl, caption, pOwner, x, y, cx, cy, styleFlags, 0)
         
  end function

As you may notice its had a few tweaks to fix issues like Win32lib not centering
a 'sub' window correctly to the screen etc..
Since I do all my programing on a 96dpi screen I code it as normal but call
dpiCreate instead of the normal win32lib 'create', if I then check on a screen
set to 120dpi it still looks good (I even tried a custom setting of 150dpi and it
still looked good).
Once I'm certain that I cope correctly with most types of controls then I'll add
it to the archive.

PeteS

21. Re: JPEG Resolution

• Posted by Pete Stoner <stoner.pete at gmail.com> Mar 16, 2006
• 490 views

Al Getz wrote:
> 
> Pete Stoner wrote:
> > 
> > Al Getz wrote:
> > > 
> > > If you want buttons to display the same size on different monitors
> > > you may wish to draw them using the dpi of the display as one of
> > > the params too.  If you want the button 1 inch wide on a 96 dpi
> > > monitor i guess you'd need 96 pixels across, while on a 180 dpi
> > > monitor you'd need 180 pixels across, so the width param in these
> > > two cases would be either 96 or 180.
> > 
> > On the subject of correcly sizing for different resolutions, its not so much
> > wanting buttons to be the same size its more that the same font will be
> > larger
> > at higher resolutions. This can mean that any text may be too large for its
> > control. As I wanted my apps to look good regardless of the users resolution
> > setting I came up with the following code.
<snip>
> 
> Hi PeteS,
> 
> 
> I was thinking that i would want my apps to have buttons (maybe other 
> stuff too) the same size on any monitor, as well as the text size.
> The reason is, what good is larger text if it doesnt fit inside
> the button?
> Any ideas?
> 
> How about a trick to get the actual size (in inches) of the monitor
> H and V ?
> 
> 
> Al
> 

Hi Al, 
I'm not sure you can have the button always the exact same size and if you did
there seems to be no way to avoid the font being increased in size. Just to
further complicate things I did see somewhere a mention that the 'pixels per
inch' stuff was sometimes talking about a *virtual* inch!!
As the fonts are larger at a higher res what the code I posted does (or best
attempt at!) is resize/reposition all the controls to match that increase
including the window size itself, otherwise your buttons get bigger and may
overlap an adjacent one or be clipped by their window.

I did lots of googling on this and it generally seems to be a mess and could not
find any one recommended way to handle it.. It seemed using Dialog units in place
of pixels was the way to go at one stage, but then I found that doesn't work very
well. My current method seems the best so far..

PeteS