Working with jpg files

Steve Lympany · Post by **Steve Lympany** » 27 Jun 2011 9:33

Hi,
Is there a better way of doing the following, eg using iStream_native, rather than working on disk?

predicates
    jpeg_picture:(string JpegFile)->picture.
clauses
    jpeg_picture(JPG)=Picture:-
                Workfile="C:\\a.bmp",
        Bitmap=bitmap::createFromFile(JPG),
            gdiplus::imageCodecInfo(JpegId, _, _, _, _, _, _, _, _, _, _, _, _) = getEncoder("BMP", gdiplus::imageEncoders),
        Bitmap:saveToFile(WorkFile, JpegId, uncheckedConvert(gdiplus::encoderParameters, 0)),
        Picture=vpi::pictLoad(WorkFile).

cheers
steve

Tonton Luc · Post by **Tonton Luc** » 27 Jun 2011 14:02

Hi,
Not sure, but maybe this can help you : http://discuss.visual-prolog.com/viewto ... hlight=jpg
http://discuss.visual-prolog.com/viewto ... hlight=jpg

Steve Lympany · Post by **Steve Lympany** » 27 Jun 2011 18:42

Hi Tonton,
Thanks, yes, I saw those, but they don't really help. I want to work with a vpi::picture, but load a jpg.

cheers
steve

Paul Cerkez · Post by **Paul Cerkez** » 29 Jun 2011 13:17

Steve,
when I looked into this a couple of years ago, what I found was to do the 'sonversion' between JPG to vip::Picture (which is BMP format), you will either need to write your own JPG file reader or lionk in a 3rd party tool.

P.

Tonton Luc · Post by **Tonton Luc** » 29 Jun 2011 15:35

Maybee you can used an invisible imageControl like :

Code: Select all

        imageControl_ctl:setImageFile("your_picture.jpg"),
        Img = imageControl_ctl:getImage(),

...and you recover a vpi::picture.

Steve Lympany · Post by **Steve Lympany** » 29 Jun 2011 18:05

Hi,
Many thanks for your thoughts.
Tonton, I assume you mean grab the picture from a window/form/screen....? It's an idea, but I think I (end-users) will lose resolution.

cheers
Steve

Steve Lympany · Post by **Steve Lympany** » 11 Jul 2011 14:31

Hello again,
Still fiddling around with this. The following code is supposed to convert a jpg to a bitmap. The reason I do it this way is that if I do it without any sizing, a 6Mb JPG converts to a 200Mb BMP. Unfortunately, the code below only produces a black bitmap.

Any ideas?

Code: Select all

predicates
        jpgToBmp :(string JpgFile).
clauses
        jpgToBmp(JpgFile):-
                Image=image::createFromFile(JpgFile),
                Graphics=graphics::createFromImage(Image),
                Bitmap=bitmap::createFromGraphics(2000,2000,Graphics), %resize
                gdiplus::imageCodecInfo(BMPId, _, _, _, _, _, _, _, _, _, _, _, _) = getEncoder("BMP", gdiplus::imageEncoders),
                BitMapFile=fileName::setExtension(JpgFile,"bmp"),
                Bitmap:saveToFile(BitMapFile, BMPId, uncheckedConvert(gdiplus::encoderParameters, 0)),
                stdio::write("\nfile ",BitMapFile," saved \n").

Thanks
regards
steve

Paul Cerkez · Post by **Paul Cerkez** » 11 Jul 2011 22:48

Steve,
when I was 1st experimenting with GDI+ and JPGs, I could never get anything but a black screen. (was in VIP6.3)

Can you get the JPG to display properly?

P.

Steve Lympany · Post by **Steve Lympany** » 12 Jul 2011 7:25

Hi Paul,
I haven't tried. I want to open a jpg and use vpi::picture (which only reads a bmp). The following works:

Code: Select all

predicates
   jpgToBmp :(string JpgFile).
clauses
   jpgToBmp(JpgFile):-
      Image=image::createFromFile(JpgFile),%or bitmap::
      gdiplus::imageCodecInfo(BMPId, _, _, _, _, _, _, _, _, _, _, _, _) = getEncoder("BMP", gdiplus::imageEncoders),
      Image:saveToFile(BitMapFile, BMPId, uncheckedConvert(gdiplus::encoderParameters, 0)).

but this can create huge bmp files of course.

cheers
steve

Paul Cerkez · Post by **Paul Cerkez** » 12 Jul 2011 21:43

Steve,
you might want to look at some JPG compression or scaling algorithms and applying them before you do the conversion to reduce the BMP file size.

P.

Steve Lympany · Post by **Steve Lympany** » 13 Jul 2011 8:49

Hi Paul,
Yes, I've tried that, and didn't get very far (after several hours). Hence the above idea,just to change the size.

Many thanks for the ideas. I'll continue to play and will post a solution if I am successful.

cheers
steve

drspro2 · Post by **drspro2** » 27 Jan 2016 15:49

In VIP 75 in the GDI plus example i can get the example working, (saving as bmp or jpg to file
with the GDI predicates)

though in another project the GDI is included but gives an error

when trying to find the the codecs info, through these predicates

it gives acces violation, i cant find what the couase is or what the difference is between the two projects

any idea is very much appreciated,

thankyou

drspro2 · Post by **drspro2** » 27 Jan 2016 16:51

I think i might have found it,

i didnt use Vargdi = gdiplus::startUp(),

GDI load and save to jpg bmp