/**************************************************************************** * graphics/nxglib/nxglib_splitline.c * * Copyright (C) 2011-2012, 2016 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. 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. * 3. Neither the name NuttX 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. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include /**************************************************************************** * Pre-Processor Definitions ****************************************************************************/ /**************************************************************************** * Private Types ****************************************************************************/ struct b16point_s { b16_t x; b16_t y; }; /**************************************************************************** * Private Data ****************************************************************************/ /**************************************************************************** * Public Data ****************************************************************************/ /**************************************************************************** * 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]: (%08x,%08x,%d),(%08x,%08x, %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]: (%08x,%08x,%d),(%08x,%08x, %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: %08x b16yoffset: %08x b16xoffset: %08x\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 (%08x,%08x),(%08x,%08x),(%08x,%08x),(%08x,%08x)\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 (%08x,%08x),(%08x,%08x),(%08x,%08x),(%08x,%08x)\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]: (%08x,%08x,%d),(%08x,%08x,%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]: (%08x,%08x,%d),(%08x,%08x,%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]: (%08x,%08x,%d),(%08x,%08x,%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]: (%08x,%08x,%d),(%08x,%08x, %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; }