73 lines
2.9 KiB
Java
73 lines
2.9 KiB
Java
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/* Copyright (C) 2000 Free Software Foundation
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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package gnu.awt.j2d;
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import java.awt.image.WritableRaster;
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import java.awt.image.ColorModel;
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/* The raster and associated properties of a mapped screen region.
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* The compositing capabilities of backends are often insufficient.
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* The backend may not support alpha blending, or may not support some
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* other special compositing rule. This means that compositing must
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* sometimes be done within the rendering pipeline. The general
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* compositing operation consists of combining new color and alpha
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* values with existing color values on the drawing surface, to find
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* the new color values for the drawing surface. The way the values
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* are combined, determines what kind of compositing operation that is
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* performed. The default compositing operation is alpha compositing.
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*
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* <p>In order to perform alpha compositing and other compositing
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* operations, we need access to the color values of the imagery that
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* has already been drawn on the drawing surface. The
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* DirectRasterGraphics interface must therefore contain methods that
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* makes it possible to gain access to the pixel values of the drawing
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* surface. The methods are modeled after the POSIX mmap() and
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* munmap() functions. But, instead of mapping and unmapping portions
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* of data from a file descriptor to memory, the methods in
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* DirectRasterGraphics maps and unmaps portions of the drawing
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* surface to data arrays within writable raster objects. A call to
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* mapRaster() will return a writable raster object, encapsulating the
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* image data of the drawing surface in the requested domain. The data
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* encapsulated by this raster object can be modified using the
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* WritableRaster API, or the data buffers can be retrieved from the
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* raster, so that the data arrays can be manipulated directly. When
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* the raster image has been modified as desired, the data can be
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* resynchronized with the drawing surface by calling mapRaster().
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*
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* <p>As with mmap() and munmap() the methods may work by direct
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* manipulation of shared memory, (i.e. the raster object directly
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* wraps the actual image data of the drawing surface), or may make a
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* private copy that is resynched when the raster is unmapped. The
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* backend may choose to implement either mechanism, and the pipeline
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* code should not care what mechanism is actually used. This design
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* allows us to make full use of speedups such as X shared memory
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* extentions when available.
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*/
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public class MappedRaster
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{
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WritableRaster raster;
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ColorModel cm;
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public MappedRaster(WritableRaster raster, ColorModel cm)
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{
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this.raster = raster;
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this.cm = cm;
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}
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public final WritableRaster getRaster()
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{
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return raster;
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}
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public final ColorModel getColorModel()
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{
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return cm;
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}
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}
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