(Lisp-HUG) Resolution of Pane -> File Writes (CAPI)

Hello Lisp Guys...

Question:   I am writing an externalized image from a pane to a 
freshly created WIN32 .BMP file and the pixels per inch resolution is 
always 96-dpi.

Is there a way to change the resolution of the output file to 
something else such as 300dpi??

I appreciate any feedback.

Regards,

Jack Harper
Secure Outcomes Inc.
Evergreen, Colorado USA






                         (gp:write-external-image 
; Write the thing to the Output File...
                           (gp:externalize-image video-display-pane
                             (gp:make-image-from-port 
video-display-pane)) output-pathname)


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Re: (Lisp-HUG) Resolution of Pane -> File Writes (CAPI)

Get a copy of IrfanView

http://www.irfanview.com/

and see if it can do it.

If so, simply call out to IrfanView with the correct command line 
parameters or script.

If your original content is 96dpi, then whatever algorithm you are going 
to use is going to have to "invent" pixels that aren't already present, 
when going to a higher res like 300dpi.  The result is going to look 
clunky unless you find some amazing smoothing / dithering algorithm.

In general, the solution is to generate the original image at infinite 
resolution, then reduce it to 96dpi or 300dpi.  This is the PDF 
approach.  See CL-PDF which works wonderfully well with CL and CAPI.  Or 
other SVG-like tools.

pt

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Re: (Lisp-HUG) Resolution of Pane -> File Writes (CAPI)

At 07:42 AM 1/30/2014, Paul Tarvydas wrote:

>Get a copy of IrfanView
>
>http://www.irfanview.com/
>
>and see if it can do it.

Thank You Paul for the suggestion.

Best that I can tell, the pixels/inch(cm) resolution of a CAPI pane 
is hardwired to reflect the physical pixels/inch(cm) count of the LCD 
monitor connected to your PC itself. You cannot change it.

CAPI has a "Screen" object that is setup at Lisp start time with that 
fixed resolution and that is used forever.

The CAPI documentation specifically says that there is exactly one 
Screen object when running under Windows.

CL-USER 1 > (setf screen (capi:convert-to-screen))
#<CAPI:COLOR-SCREEN 0 R-SCREEN>

CL-USER 2 > (capi:screen-logical-resolution screen)
96
96

CL-USER 3 >

Therefore, when I create the external file via:

                         (gp:write-external-image 
; Write the WebCam Photo to the File...
                           (gp:externalize-image video-display-pane
                             (gp:make-image-from-port 
video-display-pane)) output-pathname)

CAPI creates an external file formatted at 96 pixels/inch - and there 
is no way to change that.

I did wonder how one deals with, say, 1200bpi printers and the like - 
The CAPI printer functions allows one to define a printer as, say, 
1200bpi, but, best that I can tell, there is no way to actually 
generate 1200bpi data for the printer to print.  You actually, in my 
case, generate 96 bpi data and that is interpolated etc to fuzz it to 
1200dpi for the printer.

I do point out that I am not looking to stretch/contract an image by 
changing the pixels or the pixel count - but rather, how to generate 
a, say, 300 pixel/inch image that is one-inch on a side rather than a 
96 pixel/inch image that is about ~3 inches on a side.  The actual 
number of pixels and the pixels themselves do not change - it is 
simply a change to the pixels/inch parameter in the file header...

It looks like I will have to build an external FLI C++/WIN32/DLL 
(Yuck!) thing to do it after the external file has been generated. Double-Yuck!

Regards to the List -

Jack Harper
Secure Outcomes Inc
Evergreen, Colorado USA

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Re: (Lisp-HUG) Resolution of Pane -> File Writes (CAPI)

Great Idea Mikel and Camille -

It is obviously a hack, but it should work. I appreciate the idea.

Regards,

Jack Harper
Secure Outcomes Inc
Evergreen, Colorado USA





At 10:20 AM 1/30/2014, Camille Troillard wrote:
>Hi Jack,
>
>It's seem the image resolution is given in a BMP file as two 32 bit 
>values (for X resolution and for Y resolution, in pixel per meter) 
>at specified offsets.  Maybe you could write a small routine that 
>would overwrite the given 96 dpi value with what you need?
>
>http://en.wikipedia.org/wiki/BMP_file_format
>
>
>Best,
>Camille
>
>
>On 30 Jan 2014, at 17:44, Jack Harper <jharper@secureoutcomes.net> wrote:
>
> > I do point out that I am not looking to stretch/contract an image 
> by changing the pixels or the pixel count - but rather, how to 
> generate a, say, 300 pixel/inch image that is one-inch on a side 
> rather than a 96 pixel/inch image that is about ~3 inches on a 
> side.  The actual number of pixels and the pixels themselves do not 
> change - it is simply a change to the pixels/inch parameter in the 
> file header...


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