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- /* --COPYRIGHT--,BSD
- * Copyright (c) 2013, Texas Instruments Incorporated
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * * Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- *
- * * Neither the name of Texas Instruments Incorporated nor the names of
- * its contributors may be used to endorse or promote products derived
- * from this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
- * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
- * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
- * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- * --/COPYRIGHT--*/
-
- #include "grlib.h"
-
- //*****************************************************************************
- //
- //! \addtogroup circle_api
- //! @{
- //
- //*****************************************************************************
-
- //*****************************************************************************
- //
- //! Draws a circle.
- //!
- //! \param pContext is a pointer to the drawing context to use.
- //! \param lX is the X coordinate of the center of the circle.
- //! \param lY is the Y coordinate of the center of the circle.
- //! \param lRadius is the radius of the circle.
- //!
- //! This function draws a circle, utilizing the Bresenham circle drawing
- //! algorithm. The extent of the circle is from \e lX - \e lRadius to \e lX +
- //! \e lRadius and \e lY - \e lRadius to \e lY + \e lRadius, inclusive.
- //!
- //! \return None.
- //
- //*****************************************************************************
- void
- GrCircleDraw(const tContext *pContext, long lX, long lY, long lRadius)
- {
- long lA, lB, lD, lX1, lY1;
-
- //
- // Check the arguments.
- //
- assert(pContext);
-
- //
- // Initialize the variables that control the Bresenham circle drawing
- // algorithm.
- //
- lA = 0;
- lB = lRadius;
- lD = 3 - (2 * lRadius);
-
- //
- // Loop until the A delta is greater than the B delta, meaning that the
- // entire circle has been drawn.
- //
- while(lA <= lB)
- {
- //
- // Determine the row when subtracting the A delta.
- //
- lY1 = lY - lA;
-
- //
- // See if this row is within the clipping region.
- //
- if((lY1 >= pContext->sClipRegion.sYMin) &&
- (lY1 <= pContext->sClipRegion.sYMax))
- {
- //
- // Determine the column when subtracting the B delta.
- //
- lX1 = lX - lB;
-
- //
- // If this column is within the clipping region, then draw a pixel
- // at that position.
- //
- if((lX1 >= pContext->sClipRegion.sXMin) &&
- (lX1 <= pContext->sClipRegion.sXMax))
- {
- GrPixelDraw(pContext, lX1, lY1);
- }
-
- //
- // Determine the column when adding the B delta.
- //
- lX1 = lX + lB;
-
- //
- // If this column is within the clipping region, then draw a pixel
- // at that position.
- //
- if((lX1 >= pContext->sClipRegion.sXMin) &&
- (lX1 <= pContext->sClipRegion.sXMax))
- {
- GrPixelDraw(pContext, lX1, lY1);
- }
- }
-
- //
- // Determine the row when adding the A delta.
- //
- lY1 = lY + lA;
-
- //
- // See if this row is within the clipping region, and the A delta is
- // not zero (otherwise, it will be the same row as when the A delta was
- // subtracted).
- //
- if((lY1 >= pContext->sClipRegion.sYMin) &&
- (lY1 <= pContext->sClipRegion.sYMax) &&
- (lA != 0))
- {
- //
- // Determine the column when subtracting the B delta.
- //
- lX1 = lX - lB;
-
- //
- // If this column is within the clipping region, then draw a pixel
- // at that position.
- //
- if((lX1 >= pContext->sClipRegion.sXMin) &&
- (lX1 <= pContext->sClipRegion.sXMax))
- {
- GrPixelDraw(pContext, lX1, lY1);
- }
-
- //
- // Determine the column when adding the B delta.
- //
- lX1 = lX + lB;
-
- //
- // If this column is within the clipping region, then draw a pixel
- // at that position.
- //
- if((lX1 >= pContext->sClipRegion.sXMin) &&
- (lX1 <= pContext->sClipRegion.sXMax))
- {
- GrPixelDraw(pContext, lX1, lY1);
- }
- }
-
- //
- // Only draw the complementary pixels if the A and B deltas are
- // different (otherwise, they describe the same set of pixels).
- //
- if(lA != lB)
- {
- //
- // Determine the row when subtracting the B delta.
- //
- lY1 = lY - lB;
-
- //
- // See if this row is within the clipping region.
- //
- if((lY1 >= pContext->sClipRegion.sYMin) &&
- (lY1 <= pContext->sClipRegion.sYMax))
- {
- //
- // Determine the column when subtracting the a delta.
- //
- lX1 = lX - lA;
-
- //
- // If this column is within the clipping region, then draw a
- // pixel at that position.
- //
- if((lX1 >= pContext->sClipRegion.sXMin) &&
- (lX1 <= pContext->sClipRegion.sXMax))
- {
- GrPixelDraw(pContext, lX1, lY1);
- }
-
- //
- // Only draw the mirrored pixel if the A delta is non-zero
- // (otherwise, it will be the same pixel).
- //
- if(lA != 0)
- {
- //
- // Determine the column when adding the A delta.
- //
- lX1 = lX + lA;
-
- //
- // If this column is within the clipping region, then draw
- // a pixel at that position.
- //
- if((lX1 >= pContext->sClipRegion.sXMin) &&
- (lX1 <= pContext->sClipRegion.sXMax))
- {
- GrPixelDraw(pContext, lX1, lY1);
- }
- }
- }
-
- //
- // Determine the row when adding the B delta.
- //
- lY1 = lY + lB;
-
- //
- // See if this row is within the clipping region.
- //
- if((lY1 >= pContext->sClipRegion.sYMin) &&
- (lY1 <= pContext->sClipRegion.sYMax))
- {
- //
- // Determine the column when subtracting the A delta.
- //
- lX1 = lX - lA;
-
- //
- // If this column is within the clipping region, then draw a
- // pixel at that position.
- //
- if((lX1 >= pContext->sClipRegion.sXMin) &&
- (lX1 <= pContext->sClipRegion.sXMax))
- {
- GrPixelDraw(pContext, lX1, lY1);
- }
-
- //
- // Only draw the mirrored pixel if the A delta is non-zero
- // (otherwise, it will be the same pixel).
- //
- if(lA != 0)
- {
- //
- // Determine the column when adding the A delta.
- //
- lX1 = lX + lA;
-
- //
- // If this column is within the clipping region, then draw
- // a pixel at that position.
- //
- if((lX1 >= pContext->sClipRegion.sXMin) &&
- (lX1 <= pContext->sClipRegion.sXMax))
- {
- GrPixelDraw(pContext, lX1, lY1);
- }
- }
- }
- }
-
- //
- // See if the error term is negative.
- //
- if(lD < 0)
- {
- //
- // Since the error term is negative, adjust it based on a move in
- // only the A delta.
- //
- lD += (4 * lA) + 6;
- }
- else
- {
- //
- // Since the error term is non-negative, adjust it based on a move
- // in both the A and B deltas.
- //
- lD += (4 * (lA - lB)) + 10;
-
- //
- // Decrement the B delta.
- //
- lB -= 1;
- }
-
- //
- // Increment the A delta.
- //
- lA++;
- }
- }
-
- //*****************************************************************************
- //
- //! Draws a filled circle.
- //!
- //! \param pContext is a pointer to the drawing context to use.
- //! \param lX is the X coordinate of the center of the circle.
- //! \param lY is the Y coordinate of the center of the circle.
- //! \param lRadius is the radius of the circle.
- //!
- //! This function draws a filled circle, utilizing the Bresenham circle drawing
- //! algorithm. The extent of the circle is from \e lX - \e lRadius to \e lX +
- //! \e lRadius and \e lY - \e lRadius to \e lY + \e lRadius, inclusive.
- //!
- //! \return None.
- //
- //*****************************************************************************
- void
- GrCircleFill(const tContext *pContext, long lX, long lY, long lRadius)
- {
- long lA, lB, lD, lX1, lX2, lY1;
-
- //
- // Check the arguments.
- //
- assert(pContext);
-
- //
- // Initialize the variables that control the Bresenham circle drawing
- // algorithm.
- //
- lA = 0;
- lB = lRadius;
- lD = 3 - (2 * lRadius);
-
- //
- // Loop until the A delta is greater than the B delta, meaning that the
- // entire circle has been filled.
- //
- while(lA <= lB)
- {
- //
- // Determine the row when subtracting the A delta.
- //
- lY1 = lY - lA;
-
- //
- // See if this row is within the clipping region.
- //
- if((lY1 >= pContext->sClipRegion.sYMin) &&
- (lY1 <= pContext->sClipRegion.sYMax))
- {
- //
- // Determine the column when subtracting the B delta, and move it
- // to the left edge of the clipping region if it is to the left of
- // the clipping region.
- //
- lX1 = lX - lB;
- if(lX1 < pContext->sClipRegion.sXMin)
- {
- lX1 = pContext->sClipRegion.sXMin;
- }
-
- //
- // Determine the column when adding the B delta, and move it to the
- // right edge of the clipping region if it is to the right of the
- // clipping region.
- //
- lX2 = lX + lB;
- if(lX2 > pContext->sClipRegion.sXMax)
- {
- lX2 = pContext->sClipRegion.sXMax;
- }
-
- //
- // Draw a horizontal line if this portion of the circle is within
- // the clipping region.
- //
- if(lX1 <= lX2)
- {
- GrLineDrawH(pContext, lX1, lX2, lY1);
- }
- }
-
- //
- // Determine the row when adding the A delta.
- //
- lY1 = lY + lA;
-
- //
- // See if this row is within the clipping region, and the A delta is
- // not zero (otherwise, this describes the same row of the circle).
- //
- if((lY1 >= pContext->sClipRegion.sYMin) &&
- (lY1 <= pContext->sClipRegion.sYMax) &&
- (lA != 0))
- {
- //
- // Determine the column when subtracting the B delta, and move it
- // to the left edge of the clipping region if it is to the left of
- // the clipping region.
- //
- lX1 = lX - lB;
- if(lX1 < pContext->sClipRegion.sXMin)
- {
- lX1 = pContext->sClipRegion.sXMin;
- }
-
- //
- // Determine the column when adding the B delta, and move it to the
- // right edge of the clipping region if it is to the right of the
- // clipping region.
- //
- lX2 = lX + lB;
- if(lX2 > pContext->sClipRegion.sXMax)
- {
- lX2 = pContext->sClipRegion.sXMax;
- }
-
- //
- // Draw a horizontal line if this portion of the circle is within
- // the clipping region.
- //
- if(lX1 <= lX2)
- {
- GrLineDrawH(pContext, lX1, lX2, lY1);
- }
- }
-
- //
- // Only draw the complementary lines if the B delta is about to change
- // and the A and B delta are different (otherwise, they describe the
- // same set of pixels).
- //
- if((lD >= 0) && (lA != lB))
- {
- //
- // Determine the row when subtracting the B delta.
- //
- lY1 = lY - lB;
-
- //
- // See if this row is within the clipping region.
- //
- if((lY1 >= pContext->sClipRegion.sYMin) &&
- (lY1 <= pContext->sClipRegion.sYMax))
- {
- //
- // Determine the column when subtracting the A delta, and move
- // it to the left edge of the clipping regino if it is to the
- // left of the clipping region.
- //
- lX1 = lX - lA;
- if(lX1 < pContext->sClipRegion.sXMin)
- {
- lX1 = pContext->sClipRegion.sXMin;
- }
-
- //
- // Determine the column when adding the A delta, and move it to
- // the right edge of the clipping region if it is to the right
- // of the clipping region.
- //
- lX2 = lX + lA;
- if(lX2 > pContext->sClipRegion.sXMax)
- {
- lX2 = pContext->sClipRegion.sXMax;
- }
-
- //
- // Draw a horizontal line if this portion of the circle is
- // within the clipping region.
- //
- if(lX1 <= lX2)
- {
- GrLineDrawH(pContext, lX1, lX2, lY1);
- }
- }
-
- //
- // Determine the row when adding the B delta.
- //
- lY1 = lY + lB;
-
- //
- // See if this row is within the clipping region.
- //
- if((lY1 >= pContext->sClipRegion.sYMin) &&
- (lY1 <= pContext->sClipRegion.sYMax))
- {
- //
- // Determine the column when subtracting the A delta, and move
- // it to the left edge of the clipping region if it is to the
- // left of the clipping region.
- //
- lX1 = lX - lA;
- if(lX1 < pContext->sClipRegion.sXMin)
- {
- lX1 = pContext->sClipRegion.sXMin;
- }
-
- //
- // Determine the column when adding the A delta, and move it to
- // the right edge of the clipping region if it is to the right
- // of the clipping region.
- //
- lX2 = lX + lA;
- if(lX2 > pContext->sClipRegion.sXMax)
- {
- lX2 = pContext->sClipRegion.sXMax;
- }
-
- //
- // Draw a horizontal line if this portion of the circle is
- // within the clipping region.
- //
- if(lX1 <= lX2)
- {
- GrLineDrawH(pContext, lX1, lX2, lY1);
- }
- }
- }
-
- //
- // See if the error term is negative.
- //
- if(lD < 0)
- {
- //
- // Since the error term is negative, adjust it based on a move in
- // only the A delta.
- //
- lD += (4 * lA) + 6;
- }
- else
- {
- //
- // Since the error term is non-negative, adjust it based on a move
- // in both the A and B deltas.
- //
- lD += (4 * (lA - lB)) + 10;
-
- //
- // Decrement the B delta.
- //
- lB -= 1;
- }
-
- //
- // Increment the A delta.
- //
- lA++;
- }
- }
-
- //*****************************************************************************
- //
- // Close the Doxygen group.
- //! @}
- //
- //*****************************************************************************
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