Lossless Jpeg Functions
lazarus / 39-Graphics

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sfeinst · 2015-03-06 18:21

I'm looking for the ability to perform lossless jpg functions (like
crop and rotation).  Does anyone know of a library that will work with
Lazarus/Free Pascal?

Thanks for any information

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wp · 2015-03-30 19:12

FreeImage (http://freeimage.sourceforge.net/): Comes with a Delphi
wrapper which could work with fpc as well. Not tested by myself,
though...

Excerpt from their manual:
"FreeImage_JPEGTransform()
OperationDescriptionFIJPEG_OP_NONENo transformation (nothing is
done)FIJPEG_OP_FLIP_HHorizontal flipFIJPEG_OP_FLIP_VVertical
flipFIJPEG_OP_TRANSPOSETranspose across upper-left to lower-right
axisFIJPEG_OP_TRANSVERSETranspose across upper-right to lower-left
axisFIJPEG_OP_ROTATE_9090-degree clockwise
rotationFIJPEG_OP_ROTATE_180180-degree
rotationFIJPEG_OP_ROTATE_270270-degree clockwise rotation (or
90-degree ccw)"

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sfeinst · 2015-03-30 19:28

Thanks, I'll take a look at it.

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Mike.Cornflake · 2015-04-01 23:08

Imagemagick may also be of use...
http://www.imagemagick.org/Usage/formats/#jpg_lossless

There are fpc bindings, but I've never used them.  Usually just ship
the binary with my app and fire off commands with TProcess.

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sfeinst · 2015-04-02 00:23

Quote from: Mike.Cornflake on April 02, 2015, 01:08:50 amImagemagick
may also be of use...
http://www.imagemagick.org/Usage/formats/#jpg_lossless

There are fpc bindings, but I've never used them.  Usually just ship
the binary with my app and fire off commands with TProcess.

I am using ImageMagick that way now (for resizing, not jpeg lossless),
but wanted a Pascal way to do it.  I forgot about the bindings.  That
may be the better option.

Thanks.

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sfeinst · 2015-04-02 00:32

Actually, just looked.  IM does not do lossless rotations of jpeg
directly.  I would have to use the jpegtrans app to do it.  I don't
think there are bindings for that, though I will look for bindings for
libjpeg which comes with jpegtrans.