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author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
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committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/gnu/java/awt/java2d/PixelCoverage.java | |
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Diffstat (limited to 'libjava/classpath/gnu/java/awt/java2d/PixelCoverage.java')
-rw-r--r-- | libjava/classpath/gnu/java/awt/java2d/PixelCoverage.java | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/libjava/classpath/gnu/java/awt/java2d/PixelCoverage.java b/libjava/classpath/gnu/java/awt/java2d/PixelCoverage.java new file mode 100644 index 000000000..356021b3d --- /dev/null +++ b/libjava/classpath/gnu/java/awt/java2d/PixelCoverage.java @@ -0,0 +1,132 @@ +package gnu.java.awt.java2d; + +/** + * Stores and handles the pixel converage for a scanline. The pixel coverage + * is stored as sorted list of buckets, each of which holds information about + * the coverage for the X and Y axis. This is utilized to compute the actual + * coverage for each pixel on the scanline and finding chunks of pixels with + * equal coverage. + */ +final class PixelCoverage +{ + + /** + * One bucket in the list. + */ + private static final class Bucket + { + /** + * The X coordinate on the scanline to which this bucket belongs. + */ + int xPos; + + /** + * The X coverage. + */ + int xCov; + + /** + * The Y coverage. + */ + int yCov; + + /** + * Implements a linked list. This points to the next element of the list. + */ + Bucket next; + + /** + * Implements a linked list. This points to the previous element of the + * list. + */ + Bucket prev; + } + + /** + * The head of the sorted list of buckets. + */ + private Bucket head; + + /** + * The current bucket. We make use of the fact that the scanline converter + * always scans the scanline (and thus this list) from left to right to + * quickly find buckets or insertion points. + */ + private Bucket current; + + /** + * The bucket after the last valid bucket. Unused buckets are not thrown + * away and garbage collected. Instead, we keep them at the tail of the list + * and reuse them when necessary. + */ + private Bucket last; + + /** + * Indicates the the next scan of the scanline begins and that the next + * request will be at the beginning of this list. This makes searching and + * sorting of this list very quick. + */ + void rewind() + { + current = head; + } + + /** + * Clears the list. This does not throw away the old buckets but only + * resets the end-pointer of the list to the first element. All buckets are + * then unused and are reused when the list is filled again. + */ + void clear() + { + last = head; + } + + /** + * This adds the specified x and y coverage to the pixel at the specified + * X position. + * + * @param x the X position + * @param xc the x coverage + * @param yc the y coverage + */ + void add(int x, int xc, int yc) + { + Bucket bucket = findOrInsert(x); + bucket.xCov += xc; + bucket.yCov += yc; + } + + /** + * Finds the bucket in the list with the specified X coordinate. + * If no such bucket is found, then a new one is fetched (either a cached + * bucket from the end of the list or a newly allocated one) inserted at the + * correct position and returned. + * + * @param x the X coordinate + * + * @return a bucket to hold the coverage data + */ + private Bucket findOrInsert(int x) + { + // First search for a matching bucket. + if (head == null) + { + // Special case: the list is still empty. + head = new Bucket(); + current = head; + return head; + } + + // This performs a linear search, starting from the current bucket. + // This is reasonably efficient because access to this list is always done + // in a linear fashion and we are not more then 1 or 2 buckets away from + // the one we're looking for. + Bucket match = current; + while (match != null && match.xPos != x) + { + + } + + return match; + } +} |