JNI bridge to batik

Xavier Wielemans Thu, 09 May 2002 22:52:49 -0700

Hi all,

Involved in a big C++ software project (virtual reality engine) I tried to 
integrate batik into our system for real-time svg rendering (as it is the 
only working open-source svg renderer available - to my knowledge anyway - 
if you know better, PLEASE inform me, thx !).


Therefore I used JNI to bridge batik to our system.  I have create an 
"SVGLayer" Java class (right, the name is not very pertinent... :)  It was 
just a prototype...) which uses batik to load an svg document (in its 
constructor) and render it inside a "scene" area, based on a given scale, 
rotation, position in the scene and global scene dimensions.  To do that, 
it will compute the exact shape of the rendering result, in the scene coord 
space (by scaling/rotating/translating the svg document's rectangular 
bounding box, then clipping the resulting bounding box wrt. the scene 
boundaries) and apply to that shape the inverse transform, which gives the 
area to be rendered, in the svg document coord space (thanks to this, only 
the effectively visible part of the svg doc will be rendered).  Finally the 
rendering buffer can be retrieved (dimensions and data) as an int array 
(32-bit RGBA pixels) so you can use it in any other software to blend it in 
your own creations, for instance.

Unfortunately for us, the performance is far from enough for our 
needs.  But I hope it can at least help someone else ! ;)

Here is the SVGLayer's class javadoc + the source file.  If you are 
interested, I can also send a C++ sample prog showing how to use it through 
JNI (it works fine but it needs some extra reformatting work, so I'll do it 
only if there is interest for it).  The good news is that JNI data transfer 
doesn't diminish overall performance that much, so it is pretty usable and 
fast if you don't need a high real-time framerate.  And of course you get 
the excellent batik rendering quality (antialiasing etc.) !

BTW, it is not designed to support dynamic svg docs (scripting, 
animations,...) so I really don't know what happens if you run it on one of 
those...

Hope this helps, any comments, suggestions, critics, requests for 
additional details, build scripts... welcome !

See ya,

Willy.

Xavier Wielemans - alterface
http://www.alterface.com

SVGLayer.java
Description: Binary data

Title: SVGLayer

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com.alterface.scenario
Class SVGLayer

java.lang.Object
  |
  +--com.alterface.scenario.SVGLayer

public final class SVGLayer
extends java.lang.Object

Java SVGLayer class

Interface between Apache's Batik SVG toolkit (Java) and a native C/C++ software project (through JNI). Freely inspired from existing batik code... ;)

Constructor Summary
`SVGLayer(java.lang.String svgFile)` Constructs a new SVGLayer.

Method Summary
`int`	`getDataBufferHeight()` Gets REAL data buffer height.
`int`	`getDataBufferWidth()` Gets REAL data buffer width.
`int`	`getDataBufferXOffset()` Gets data buffer offset in the X direction.
`int`	`getDataBufferYOffset()` Gets the layer's data buffer offset in the Y direction.
`int`	`getDocHeight()` Gets the document height
`int`	`getDocWidth()` Gets the document width
`int`	`getImgHeight()` Gets the current rendered image height
`int`	`getImgWidth()` Gets the current rendered image width
`int`	`getImgXOffset()` Gets image offset in the X direction.
`int`	`getImgYOffset()` Gets image offset in the Y direction.
`static void`	`main(java.lang.String[] args)` Main method (for testing purposes only)
`int[]`	`render()` Renders the SVG layer.
`void`	`setRotation(double angle)` Sets the layer's rotation angle
`void`	`setScale(java.awt.geom.Point2D.Double scale)` Sets the layer's scale
`void`	`setScenePosition(java.awt.Point position)` Sets the layer position in the scene.
`void`	`setSceneSize(java.awt.Point size)` Sets the scene size.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SVGLayer

public SVGLayer(java.lang.String svgFile)

Constructs a new SVGLayer.
Parameters:: svgFile - source file containing the SVG description

Method Detail

main

public static final void main(java.lang.String[] args)

Main method (for testing purposes only)

setScale

public void setScale(java.awt.geom.Point2D.Double scale)

Sets the layer's scale

Parameters:: scale - the new x/y scale at which the layer is to be rendered

setRotation

public void setRotation(double angle)

Sets the layer's rotation angle

Parameters:: angle - the new rotation angle at which the layer is to be rendered

setSceneSize

public void setSceneSize(java.awt.Point size)

Sets the scene size. This information, along with the scene position of the layer, will be used to clip document shape so that only visible parts will actually be rendered.

Parameters:: size - the new x/y size of the scene in which the svg document is to be rendered.

setScenePosition

public void setScenePosition(java.awt.Point position)

Sets the layer position in the scene. This information, along with the scene size, will be used to clip document shape so that only visible parts will actually be rendered.

Parameters:: position - the new x/y position of the document's center point in the scene.

getDocWidth

public int getDocWidth()

Gets the document width

Returns:: the source document's width (as an int)

getDocHeight

public int getDocHeight()

Gets the document height

Returns:: the source document's layer's height (as an int)

getImgWidth

public int getImgWidth()

Gets the current rendered image width

Returns:: the current width of the rendered image, taking into account current scale/rotation, scene size and scene position.

getImgHeight

public int getImgHeight()

Gets the current rendered image height

Returns:: the current height of the rendered image, taking into account current scale/rotation, scene size and scene position.

getDataBufferWidth

public int getDataBufferWidth()

Gets REAL data buffer width. The data buffer is often actually larger than the image ! In that case, the data buffer offset indicates the X/Y translation between top-left corners of image and data buffer. so that both origins match. NB: updated at each rendering.

Returns:: the actual width of the data buffer returned by 'render()'.

getDataBufferHeight

public int getDataBufferHeight()

Gets REAL data buffer height. The data buffer is often actually larger than the image ! In that case, the data buffer offset indicates the X/Y translation between top-left corners of image and data buffer. NB: updated at each rendering.

Returns:: the actual height of the data buffer returned by 'render()'.

getDataBufferXOffset

public int getDataBufferXOffset()

Gets data buffer offset in the X direction. It is equal to the X position of the image top-left corner pixel in the data buffer. NB: updated at each rendering.

Returns:: the image X offset into the data buffer

getDataBufferYOffset

public int getDataBufferYOffset()

Gets the layer's data buffer offset in the Y direction. It is equal to the Y position of the image top-left corner pixel in the data buffer. NB: updated at each rendering.

Returns:: the image Y offset into the data buffer

getImgXOffset

public int getImgXOffset()

Gets image offset in the X direction. It is equal to the X position of the document center in the image. NB: updated at each rendering.

Returns:: the document center X offset into the image

getImgYOffset

public int getImgYOffset()

Gets image offset in the Y direction. It is equal to the Y position of the document center in the image. NB: updated at each rendering.

Returns:: the document center Y offset into the image

render

public int[] render()

Renders the SVG layer.