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incubator-nuttx/libs/libnx/nxglib/nxglib_splitline.c

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/****************************************************************************
* libs/libnx/nxglib/nxglib_splitline.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <string.h>
#include <errno.h>
#include <inttypes.h>
#include <stdlib.h>
#include <debug.h>
#include <nuttx/nx/nxglib.h>
/****************************************************************************
* Private Types
****************************************************************************/
struct b16point_s
{
b16_t x;
b16_t y;
};
/****************************************************************************
* Private Functions
****************************************************************************/
static b16_t nxgl_interpolate(b16_t x, b16_t dy, b16_t dxdy)
{
b16_t dx = b16mulb16(dy, dxdy);
return x + dx;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxgl_splitline
*
* Description:
* In the general case, a line with width can be represented as a
* parallelogram with a triangle at the top and bottom. Triangles and
* parallelograms are both degenerate versions of a trapeziod. This
* function breaks a wide line into triangles and trapezoids. This
* function also detects other degenerate cases:
*
* 1. If y1 == y2 then the line is horizontal and is better represented
* as a rectangle.
* 2. If x1 == x2 then the line is vertical and also better represented
* as a rectangle.
* 3. If the width of the line is 1, then there are no triangles at the
* top and bottome (this may also be the case if the width is narrow
* and the line is near vertical).
* 4. If the line is oriented is certain angles, it may consist only of
* the upper and lower triangles with no trapezoid in between. In
* this case, 3 trapezoids will be returned, but traps[1] will be
* degenerate.
*
* Input Parameters:
* vector - A pointer to the vector described the line to be drawn.
* traps - A pointer to a array of trapezoids (size 3).
* rect - A pointer to a rectangle.
*
* Returned Value:
* 0: Line successfully broken up into three trapezoids. Values in
* traps[0], traps[1], and traps[2] are valid.
* 1: Line successfully represented by one trapezoid. Value in traps[1]
* is valid.
* 2: Line successfully represented by one rectangle. Value in rect is
* valid
* <0: On errors, a negated errno value is returned.
*
****************************************************************************/
int nxgl_splitline(FAR struct nxgl_vector_s *vector,
FAR struct nxgl_trapezoid_s *traps,
FAR struct nxgl_rect_s *rect,
nxgl_coord_t linewidth)
{
struct nxgl_vector_s line;
nxgl_coord_t iheight;
nxgl_coord_t iwidth;
nxgl_coord_t iyoffset;
struct b16point_s quad[4];
b16_t b16xoffset;
b16_t b16yoffset;
b16_t b16dxdy;
b16_t angle;
b16_t cosangle;
b16_t sinangle;
b16_t b16x;
b16_t b16y;
ginfo("vector: (%d,%d)->(%d,%d) linewidth: %d\n",
vector->pt1.x, vector->pt1.y, vector->pt2.x, vector->pt2.y,
linewidth);
/* First, check the linewidth */
if (linewidth < 1)
{
return -EINVAL;
}
/* Then make sure that the start position of the line is above the end
* position of the line... in raster order.
*/
if (vector->pt1.y < vector->pt2.y)
{
/* Vector is already in raster order */
memcpy(&line, vector, sizeof(struct nxgl_vector_s));
}
else if (vector->pt1.y > vector->pt2.y)
{
/* Swap the top and bottom */
line.pt1.x = vector->pt2.x;
line.pt1.y = vector->pt2.y;
line.pt2.x = vector->pt1.x;
line.pt2.y = vector->pt1.y;
}
else /* if (vector->pt1.y == vector->pt2.y) */
{
/* First degenerate case: The line is horizontal. */
if (vector->pt1.x < vector->pt2.x)
{
rect->pt1.x = vector->pt1.x;
rect->pt2.x = vector->pt2.x;
}
else
{
rect->pt1.x = vector->pt2.x;
rect->pt2.x = vector->pt1.x;
}
/* The height of the rectangle is the width of the line, half above
* and half below.
*/
rect->pt1.y = vector->pt1.y - (linewidth >> 1);
rect->pt2.y = rect->pt1.y + linewidth - 1;
ginfo("Horizontal rect: (%d,%d),(%d,%d)\n",
rect->pt1.x, rect->pt1.y, rect->pt2.x, rect->pt2.y);
return 2;
}
/* Check if the line is vertical */
if (line.pt1.x == line.pt2.x)
{
/* Second degenerate case: The line is vertical. */
rect->pt1.y = line.pt1.y;
rect->pt2.y = line.pt2.y;
rect->pt1.x = line.pt1.x - (linewidth >> 1);
rect->pt2.x = rect->pt1.x + linewidth - 1;
ginfo("Vertical rect: (%d,%d),(%d,%d)\n",
rect->pt1.x, rect->pt1.y, rect->pt2.x, rect->pt2.y);
return 2;
}
/* The final degenerate case */
if (linewidth == 1 &&
abs(line.pt2.x - line.pt1.x) < (line.pt2.y - line.pt1.y))
{
/* A close to vertical line of width 1 is basically
* a single parallelogram of width 1.
*/
traps[1].top.x1 = itob16(line.pt1.x);
traps[1].top.x2 = traps[1].top.x1;
traps[1].top.y = line.pt1.y;
traps[1].bot.x1 = itob16(line.pt2.x);
traps[1].bot.x2 = traps[1].bot.x1;
traps[1].bot.y = line.pt2.y;
ginfo("Vertical traps[1]: (%08" PRIx32 ",%08" PRIx32 ",%d),"
"(%08" PRIx32 ",%08" PRIx32 ", %d)\n",
traps[1].top.x1, traps[1].top.x2, traps[1].top.y,
traps[1].bot.x1, traps[1].bot.x2, traps[1].bot.y);
return 1;
}
else if (linewidth == 1)
{
b16_t pixels_per_row;
/* Close to horizontal line of width 1 */
pixels_per_row = itob16(line.pt2.x - line.pt1.x) /
(line.pt2.y - line.pt1.y);
traps[1].top.x1 = itob16(line.pt1.x);
traps[1].top.x2 = traps[1].top.x1 + pixels_per_row;
traps[1].top.y = line.pt1.y;
traps[1].bot.x2 = itob16(line.pt2.x);
traps[1].bot.x1 = traps[1].bot.x2 - pixels_per_row;
traps[1].bot.y = line.pt2.y;
if (pixels_per_row < 0)
{
b16_t tmp;
tmp = traps[1].top.x2;
traps[1].top.x2 = traps[1].top.x1;
traps[1].top.x1 = tmp;
tmp = traps[1].bot.x2;
traps[1].bot.x2 = traps[1].bot.x1;
traps[1].bot.x1 = tmp;
}
ginfo("Horizontal traps[1]: (%08" PRIx32 ",%08" PRIx32 ",%d),"
"(%08" PRIx32 ",%08" PRIx32 ", %d)\n",
traps[1].top.x1, traps[1].top.x2, traps[1].top.y,
traps[1].bot.x1, traps[1].bot.x2, traps[1].bot.y);
return 1;
}
/* Okay, then what remains is interesting.
*
* iheight = |y2 - y1|
* iwidth = |x2 - x1|
*/
iheight = line.pt2.y - line.pt1.y + 1;
if (line.pt1.x < line.pt2.x)
{
iwidth = line.pt2.x - line.pt1.x + 1;
}
else
{
iwidth = line.pt1.x - line.pt2.x + 1;
}
/* Applying the line width to the line results in a rotated, rectangle.
* Get the Y offset from an end of the original thin line to a corner of
* the fat line.
*
* Angle of line: angle = atan2(iheight, iwidth)
* Y offset from line: b16yoffset = linewidth * cos(angle)
*
* For near verical lines, b16yoffset is be nearly zero. For near
* horizontal lines, b16yOffset is be about the same as linewidth.
*/
angle = b16atan2(itob16(iheight), itob16(iwidth));
cosangle = b16cos(angle);
b16yoffset = (linewidth * cosangle + 1) >> 1;
/* Get the X offset from an end of the original thin line to a corner of
* the fat line.
*
* For near vertical lines, b16xoffset is about the same as linewidth.
* For near horizontal lines, b16xoffset is nearly zero.
*/
sinangle = b16sin(angle);
b16xoffset = (linewidth * sinangle + 1) >> 1;
ginfo("height: %d width: %d angle: %08" PRIx32 " "
"b16yoffset: %08" PRIx32 " b16xoffset: %08" PRIx32 "\n",
iheight, iwidth, angle, b16yoffset, b16xoffset);
/* Now we know all four points of the rotated rectangle */
iyoffset = b16toi(b16yoffset + b16HALF);
if (iyoffset > 0)
{
/* Get the Y positions of each point */
b16y = itob16(line.pt1.y);
quad[0].y = b16y - b16yoffset;
quad[1].y = b16y + b16yoffset;
b16y = itob16(line.pt2.y);
quad[2].y = b16y - b16yoffset;
quad[3].y = b16y + b16yoffset;
if (line.pt1.x < line.pt2.x)
{
/* Line is going "south east". Get the X positions of each point */
b16x = itob16(line.pt1.x);
quad[0].x = b16x + b16xoffset;
quad[1].x = b16x - b16xoffset;
b16x = itob16(line.pt2.x);
quad[2].x = b16x + b16xoffset;
quad[3].x = b16x - b16xoffset;
ginfo("Southeast: quad (%08" PRIx32 ",%08" PRIx32 "),"
"(%08" PRIx32 ",%08" PRIx32 "),"
"(%08" PRIx32 ",%08" PRIx32 "),"
"(%08" PRIx32 ",%08" PRIx32 ")\n",
quad[0].x, quad[0].y, quad[1].x, quad[1].y,
quad[2].x, quad[2].y, quad[3].x, quad[3].y);
/* Now we can form the trapezoids. The top of the first trapezoid
* (triangle) is at quad[0]
*/
traps[0].top.x1 = quad[0].x;
traps[0].top.x2 = quad[0].x;
traps[0].top.y = b16toi(quad[0].y + b16HALF);
/* The bottom of the first trapezoid (triangle) may be either at
* quad[1] or quad[2], depending upon orientation.
*/
if (quad[1]. y < quad[2].y)
{
/* quad[1] is at the bottom left of the triangle. Interpolate
* to get the corresponding point on the right side.
*
* Interpolation is from quad[0] along the line
* quad[0]->quad[2] which as the same slope as the line
* (positive)
*/
b16dxdy = itob16(iwidth) / iheight;
traps[0].bot.x1 = quad[1].x;
traps[0].bot.x2 = nxgl_interpolate(quad[0].x,
quad[1].y - quad[0].y,
b16dxdy);
traps[0].bot.y = b16toi(quad[1].y + b16HALF);
/* quad[1] is at the top left of the second trapezoid.
* quad[2} is at the bottom right of the second trapezoid.
* Interpolate to get corresponding point on the left side.
*
* Interpolation is from quad[1] along the line
* quad[1]->quad[3] which as the same slope as the line
* (positive)
*/
traps[1].top.x1 = traps[0].bot.x1;
traps[1].top.x2 = traps[0].bot.x2;
traps[1].top.y = traps[0].bot.y;
traps[1].bot.x1 = nxgl_interpolate(traps[1].top.x1,
quad[2].y - quad[1].y,
b16dxdy);
traps[1].bot.x2 = quad[2].x;
traps[1].bot.y = b16toi(quad[2].y + b16HALF);
}
else
{
/* quad[2] is at the bottom right of the triangle. Interpolate
* to get the corresponding point on the left side.
*
* Interpolation is from quad[0] along the line
* quad[0]->quad[1] which orthogonal to the slope of the line
* (and negative)
*/
b16dxdy = -itob16(iheight) / iwidth;
traps[0].bot.x1 = nxgl_interpolate(quad[0].x,
quad[2].y - quad[0].y,
b16dxdy);
traps[0].bot.x2 = quad[2].x;
traps[0].bot.y = b16toi(quad[2].y + b16HALF);
/* quad[2] is at the top right of the second trapezoid.
* quad[1} is at the bottom left of the second trapezoid.
* Interpolate to get corresponding point on the right side.
*
* Interpolation is from quad[2] along the line
* quad[2]->quad[3] which as the same slope as the previous
* interpolation.
*/
traps[1].top.x1 = traps[0].bot.x1;
traps[1].top.x2 = traps[0].bot.x2;
traps[1].top.y = traps[0].bot.y;
traps[1].bot.x1 = quad[1].x;
traps[1].bot.x2 = nxgl_interpolate(traps[1].top.x2,
quad[1].y - quad[2].y,
b16dxdy);
traps[1].bot.y = b16toi(quad[1].y + b16HALF);
}
/* The final trapezond (triangle) at the bottom is new well
* defined
*/
traps[2].top.x1 = traps[1].bot.x1;
traps[2].top.x2 = traps[1].bot.x2;
traps[2].top.y = traps[1].bot.y;
traps[2].bot.x1 = quad[3].x;
traps[2].bot.x2 = quad[3].x;
traps[2].bot.y = b16toi(quad[3].y + b16HALF);
}
else
{
/* Get the X positions of each point */
b16x = itob16(line.pt1.x);
quad[0].x = b16x - b16xoffset;
quad[1].x = b16x + b16xoffset;
b16x = itob16(line.pt2.x);
quad[2].x = b16x - b16xoffset;
quad[3].x = b16x + b16xoffset;
ginfo("Southwest: quad (%08" PRIx32 ",%08" PRIx32 "),"
"(%08" PRIx32 ",%08" PRIx32 "),"
"(%08" PRIx32 ",%08" PRIx32 "),"
"(%08" PRIx32 ",%08" PRIx32 ")\n",
quad[0].x, quad[0].y, quad[1].x, quad[1].y,
quad[2].x, quad[2].y, quad[3].x, quad[3].y);
/* Now we can form the trapezoids. The top of the first trapezoid
* (triangle) is at quad[0]
*/
traps[0].top.x1 = quad[0].x;
traps[0].top.x2 = quad[0].x;
traps[0].top.y = b16toi(quad[0].y + b16HALF);
/* The bottom of the first trapezoid (triangle) may be either at
* quad[1] or quad[2], depending upon orientation.
*/
if (quad[1].y < quad[2].y)
{
/* quad[1] is at the bottom right of the triangle. Interpolate
* to get the corresponding point on the left side.
*
* Interpolation is from quad[0] along the line
* quad[0]->quad[2] which as the same slope as the line
* (negative)
*/
b16dxdy = -itob16(iwidth) / iheight;
traps[0].bot.x1 = nxgl_interpolate(traps[0].top.x1,
quad[1].y - quad[0].y,
b16dxdy);
traps[0].bot.x2 = quad[1].x;
traps[0].bot.y = b16toi(quad[1].y + b16HALF);
/* quad[1] is at the top right of the second trapezoid.
* quad[2} is at the bottom left of the second trapezoid.
* Interpolate to get corresponding point on the right side.
*
* Interpolation is from quad[1] along the line
* quad[1]->quad[3] which as the same slope as the line
* (negative)
*/
traps[1].top.x1 = traps[0].bot.x1;
traps[1].top.x2 = traps[0].bot.x2;
traps[1].top.y = traps[0].bot.y;
traps[1].bot.x1 = quad[2].x;
traps[1].bot.x2 = nxgl_interpolate(traps[1].top.x2,
quad[2].y - quad[1].y,
b16dxdy);
traps[1].bot.y = b16toi(quad[2].y + b16HALF);
}
else
{
/* quad[2] is at the bottom left of the triangle. Interpolate
* to get the corresponding point on the right side.
*
* Interpolation is from quad[0] along the line
* quad[0]->quad[1] which orthogonal to the slope of the line
* (and positive)
*/
b16dxdy = itob16(iheight) / iwidth;
traps[0].bot.x1 = quad[2].x;
traps[0].bot.x2 = nxgl_interpolate(traps[0].top.x2,
quad[2].y - quad[0].y,
b16dxdy);
traps[0].bot.y = b16toi(quad[2].y + b16HALF);
/* quad[2] is at the top left of the second trapezoid.
* quad[1} is at the bottom right of the second trapezoid.
* Interpolate to get corresponding point on the left side.
*
* Interpolation is from quad[2] along the line
* quad[2]->quad[3] which as the same slope as the previous
* interpolation.
*/
traps[1].top.x1 = traps[0].bot.x1;
traps[1].top.x2 = traps[0].bot.x2;
traps[1].top.y = traps[0].bot.y;
traps[1].bot.x1 = nxgl_interpolate(traps[1].top.x1,
quad[1].y - quad[2].y,
b16dxdy);
traps[1].bot.x2 = quad[1].x;
traps[1].bot.y = b16toi(quad[1].y + b16HALF);
}
/* The final trapezond (triangle) at the bottom is new well
* defined
*/
traps[2].top.x1 = traps[1].bot.x1;
traps[2].top.x2 = traps[1].bot.x2;
traps[2].top.y = traps[1].bot.y;
traps[2].bot.x1 = quad[3].x;
traps[2].bot.x2 = quad[3].x;
traps[2].bot.y = b16toi(quad[3].y + b16HALF);
}
ginfo("traps[0]: (%08" PRIx32 ",%08" PRIx32 ",%d),"
"(%08" PRIx32 ",%08" PRIx32 ",%d)\n",
traps[0].top.x1, traps[0].top.x2, traps[0].top.y,
traps[0].bot.x1, traps[0].bot.x2, traps[0].bot.y);
ginfo("traps[1]: (%08" PRIx32 ",%08" PRIx32 ",%d),"
"(%08" PRIx32 ",%08" PRIx32 ",%d)\n",
traps[1].top.x1, traps[1].top.x2, traps[1].top.y,
traps[1].bot.x1, traps[1].bot.x2, traps[1].bot.y);
ginfo("traps[2]: (%08" PRIx32 ",%08" PRIx32 ",%d),"
"(%08" PRIx32 ",%08" PRIx32 ",%d)\n",
traps[2].top.x1, traps[2].top.x2, traps[2].top.y,
traps[2].bot.x1, traps[2].bot.x2, traps[2].bot.y);
return 0;
}
/* The line is too vertical to have any significant triangular top or
* bottom. Just return the center parallelogram.
*/
traps[1].top.x1 = itob16(line.pt1.x - (linewidth >> 1));
traps[1].top.x2 = traps[1].top.x1 + itob16(linewidth - 1);
traps[1].top.y = line.pt1.y;
traps[1].bot.x1 = itob16(line.pt2.x - (linewidth >> 1));
traps[1].bot.x2 = traps[1].bot.x1 + itob16(linewidth - 1);
traps[1].bot.y = line.pt2.y;
ginfo("Horizontal traps[1]: (%08" PRIx32 ",%08" PRIx32 ",%d),"
"(%08" PRIx32 ",%08" PRIx32 ", %d)\n",
traps[1].top.x1, traps[1].top.x2, traps[1].top.y,
traps[1].bot.x1, traps[1].bot.x2, traps[1].bot.y);
return 1;
}
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