Replace invalid characters with HTML entities
— with — ’ with ’ + with + × with x ç with ç “ with “ ” with ” ‘ with ‘ • with • – with - µ with µ † with † Fix C++ θ with θ Yen symbol instead of times Fix broken apos Bullet again E-circumflex
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James Gregory
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353 changed files with 5091 additions and 5091 deletions
38
41-02.html
38
41-02.html
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@ -48,47 +48,47 @@
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<!-- CODE //-->
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<PRE>
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/* Color-fills a convex polygon. All vertices are offset by (XOffset, YOffset).
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“Convex” means “monotone with respect to a vertical line”; that is, every
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“Convex” means “monotone with respect to a vertical line”; that is, every
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horizontal line drawn through the polygon at any point would cross exactly two
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active edges (neither horizontal lines nor zero-length edges count as active
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edges; both are acceptable anywhere in the polygon). Right & left edges may
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cross (polygons may be nonsimple). Polygons that are not convex according to
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this definition won’t be drawn properly. (Yes, “convex” is a lousy name for
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this type of polygon, but it’s convenient; use “monotone-vertical” if it makes
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this definition won’t be drawn properly. (Yes, “convex” is a lousy name for
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this type of polygon, but it’s convenient; use “monotone-vertical” if it makes
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you happier!)
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*******************************************************************
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NOTE: the low-level drawing routine, DrawHorizontalLineList, must be able to
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reverse the edges, if necessary to make the correct edge left edge. It must
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also expect right edge to be specified in +1 format (the X coordinate is 1 past
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also expect right edge to be specified in +1 format (the X coordinate is 1 past
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highest coordinate to draw). In both respects, this differs from low-level
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drawing routines presented in earlier columns; changes are necessary to make it
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possible to draw nonsimple monotone-vertical polygons; that in turn makes it
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possible to use Jim Kent’s test for monotone-vertical polygons.
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possible to use Jim Kent’s test for monotone-vertical polygons.
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*******************************************************************
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Returns 1 for success, 0 if memory allocation failed */
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#include <stdio.h>
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#include <math.h>
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#include <stdlib.h>
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#include “polygon.h”
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#include “polygon.h”
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/* Advances the index by one vertex forward through the vertex list,
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wrapping at the end of the list */
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#define INDEX_FORWARD(Index) \
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Index = (Index + 1) % VertexList->Length;
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Index = (Index + 1) % VertexList->Length;
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/* Advances the index by one vertex backward through the vertex list,
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wrapping at the start of the list */
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#define INDEX_BACKWARD(Index) \
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Index = (Index - 1 + VertexList->Length) % VertexList->Length;
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Index = (Index - 1 + VertexList->Length) % VertexList->Length;
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/* Advances the index by one vertex either forward or backward through
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the vertex list, wrapping at either end of the list */
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#define INDEX_MOVE(Index,Direction) \
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if (Direction > 0) \
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Index = (Index + 1) % VertexList->Length; \
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Index = (Index + 1) % VertexList->Length; \
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else \
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Index = (Index - 1 + VertexList->Length) % VertexList->Length;
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Index = (Index - 1 + VertexList->Length) % VertexList->Length;
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extern void ScanEdge(int, int, int, int, int, int, struct HLine **);
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extern void DrawHorizontalLineList(struct HLineList *, int);
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@ -109,7 +109,7 @@ int FillMonotoneVerticalPolygon(struct PointListHeader * VertexList,
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if (VertexList->Length == 0)
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return(1); /* reject null polygons */
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MaxPoint_Y = MinPoint_Y = VertexPtr[MinIndex = MaxIndex = 0].Y;
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for (i = 1; i < VertexList->Length; i++) {
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for (i = 1; i < VertexList->Length; i++) {
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if (VertexPtr[i].Y < MinPoint_Y)
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MinPoint_Y = VertexPtr[MinIndex = i].Y; /* new top */
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else if (VertexPtr[i].Y > MaxPoint_Y)
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@ -118,14 +118,14 @@ int FillMonotoneVerticalPolygon(struct PointListHeader * VertexList,
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/* Set the # of scan lines in the polygon, skipping the bottom edge */
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if ((WorkingHLineList.Length = MaxPoint_Y - MinPoint_Y) <= 0)
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return(1); /* there’s nothing to draw, so we’re done */
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WorkingHLineList.YStart = YOffset + MinPoint_Y;
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return(1); /* there’s nothing to draw, so we’re done */
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WorkingHLineList.YStart = YOffset + MinPoint_Y;
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/* Get memory in which to store the line list we generate */
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if ((WorkingHLineList.HLinePtr =
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(struct HLine *) (malloc(sizeof(struct HLine) *
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WorkingHLineList.Length))) == NULL)
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return(0); /* couldn’t get memory for the line list */
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return(0); /* couldn’t get memory for the line list */
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/* Scan the first edge and store the boundary points in the list */
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/* Initial pointer for storing scan converted first-edge coords */
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@ -135,9 +135,9 @@ int FillMonotoneVerticalPolygon(struct PointListHeader * VertexList,
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/* Scan convert each line in the first edge from top to bottom */
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do {
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INDEX_BACKWARD(CurrentIndex);
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ScanEdge(VertexPtr[PreviousIndex].X + XOffset,
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ScanEdge(VertexPtr[PreviousIndex].X + XOffset,
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VertexPtr[PreviousIndex].Y,
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VertexPtr[CurrentIndex].X + XOffset,
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VertexPtr[CurrentIndex].X + XOffset,
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VertexPtr[CurrentIndex].Y, 1, 0, &EdgePointPtr);
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PreviousIndex = CurrentIndex;
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} while (CurrentIndex != MaxIndex);
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@ -148,9 +148,9 @@ int FillMonotoneVerticalPolygon(struct PointListHeader * VertexList,
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/* Scan convert the second edge, top to bottom */
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do {
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INDEX_FORWARD(CurrentIndex);
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ScanEdge(VertexPtr[PreviousIndex].X + XOffset,
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ScanEdge(VertexPtr[PreviousIndex].X + XOffset,
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VertexPtr[PreviousIndex].Y,
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VertexPtr[CurrentIndex].X + XOffset,
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VertexPtr[CurrentIndex].X + XOffset,
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VertexPtr[CurrentIndex].Y, 0, 0, &EdgePointPtr);
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PreviousIndex = CurrentIndex;
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} while (CurrentIndex != MaxIndex);
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@ -158,7 +158,7 @@ int FillMonotoneVerticalPolygon(struct PointListHeader * VertexList,
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/* Draw the line list representing the scan converted polygon */
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DrawHorizontalLineList(&WorkingHLineList, Color);
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/* Release the line list’s memory and we’re successfully done */
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/* Release the line list’s memory and we’re successfully done */
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free(WorkingHLineList.HLinePtr);
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return(1);
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}
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