commit: Infrastructure for tighly wrapped images.

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CVS: Committing in .
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CVS: Modified Files:
CVS: src/af/gr/cocoa/gr_CocoaImage.h
CVS: src/af/gr/cocoa/gr_CocoaImage.mm
CVS: src/af/gr/unix/gr_UnixImage.cpp src/af/gr/unix/gr_UnixImage.h
CVS: src/af/gr/win/gr_Win32Image.cpp src/af/gr/win/gr_Win32Image.h
CVS: src/af/gr/xp/gr_Image.cpp src/af/gr/xp/gr_Image.h
CVS: src/af/gr/xp/gr_VectorImage.cpp src/af/gr/xp/gr_VectorImage.h
CVS: src/af/xap/unix/xap_UnixPSGraphics.cpp
CVS: src/af/xap/unix/xap_UnixPSImage.cpp
CVS: src/af/xap/unix/xap_UnixPSImage.h
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Some infrastructure for tight wrapped images.

This commit provides a lot of the infrastructure needed for tight text
wrapping around images and objects.

This is where the text encroaches into the rectangular box which encloses
images with large areas of transparency such as are often found in clip
art collections and in particular in the open clip art collect at:

I must admit part of my reason for working on this code is because I want
abiword screenshots to be featured along side OOo shots on that site. I
also remember being really impressed when I first saw this feature in MS
Word 97 and wondered how they did it. So here we go :-)

The way I intend to implement this is to increase the length of the lines
placed around wrapped images to reflect the transparency of the object.

So we need to work out if an image has transparency and where the first
non-transparent pixel is on each row of the image.

To do this we need two additional platform-specific methods for the
GR_Image class. These are:

virtual bool isTransparentAt(UT_sint32 x, UT_sint32 y) =0;
virtual bool hasAlpha (void) const = 0;

These are pure virtual in the GR_Image base class. I've implemented these
for the Unix framework and have placed code that asserts in the Win32 and
Cocoa builds. I haven't tested these. So once again, my apologies if these
break those builds - it should be easy to fix though.

The method "hasAlpha" simply returns true if there is any transparency in
the image. If there isn't all the rest of the code is shorted circuited.

The method "isTransparentAt(x,y)" returns true if the pixel at the device
location (x,y) is pure transparent. This is a simple method that just
calculates the the location of the pixel at (x,y) and determines if it's
totally transparent.

With these platform-specific methods we can now implement the XP methods
in GR_Image. These are:
        void GenerateOutline(void);
        void DestroyOutline(void);
        UT_sint32 GetOffsetFromLeft(GR_Graphics * pG, UT_sint32 pad, UT_sint32
yTop, UT_sint32 height);
        UT_sint32 GetOffsetFromRight(GR_Graphics * pG, UT_sint32 pad, UT_sint32
yTop, UT_sint32 height);

        bool isOutLinePresent(void) const
          { return (m_vecOutLine.getItemCount() > 0);}

The GenerateOutline method scans the image from the left and right sides
for the first non-transparent pixel at each row of the image. As it finds
this pixel it records it's location in the simple little class

class ABI_EXPORT GR_Image_Point
{
public:
  GR_Image_Point(void) : m_iX(0),m_iY(0)
    {}
  UT_sint32 m_iX;
  UT_sint32 m_iY;
};

then saves each point in the vector

        UT_GenericVector<GR_Image_Point *> m_vecOutLine;

This vector contains the outline of the non-transparent portions of the
image. The "DestroyOutline(void)" method simply clears out this vector.

The methods:

UT_sint32 GetOffsetFromLeft(GR_Graphics * pG, UT_sint32 pad, UT_sint32
yTop, UT_sint32 height);
        UT_sint32 GetOffsetFromRight(GR_Graphics * pG, UT_sint32 pad, UT_sint32
yTop, UT_sint32 height);

Are what will be actually used to implement the tight wrapping feature. I
will implement these by intelligently scanning the the outline and
determining the closest approach of each pixel to the line segment given.
I've worked out the maths for this but it's not implemented yet.

I'll send another post with this info.

Cheers

Martin
Received on Fri Feb 25 00:45:45 2005