gd.c

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	{			/* No room for more colors */
	  return ct;		/* Return closest available color */
	}
      im->colorsTotal++;
    }
  im->red[op] = r;
  im->green[op] = g;
  im->blue[op] = b;
  im->alpha[op] = a;
  im->open[op] = 0;
  return op;			/* Return newly allocated color */
}

void gdImageColorDeallocate (gdImagePtr im, int color)
{
	if (im->trueColor) {
		return;
	}
	/* Mark it open. */
	im->open[color] = 1;
}

void gdImageColorTransparent (gdImagePtr im, int color)
{
	if (!im->trueColor) {
		if (im->transparent != -1) {
			im->alpha[im->transparent] = gdAlphaOpaque;
		}
		if (color > -1 && color<im->colorsTotal && color<=gdMaxColors) {
			im->alpha[color] = gdAlphaTransparent;
		} else {
			return;
		}
	}
	im->transparent = color;
}

void gdImagePaletteCopy (gdImagePtr to, gdImagePtr from)
{
	int i;
	int x, y, p;
	int xlate[256];
	if (to->trueColor || from->trueColor) {
		return;
	}

	for (i = 0; i < 256; i++) {
		xlate[i] = -1;
	}

	for (x = 0; x < to->sx; x++) {
		for (y = 0; y < to->sy; y++) {
			p = gdImageGetPixel(to, x, y);
			if (xlate[p] == -1) {
				/* This ought to use HWB, but we don't have an alpha-aware version of that yet. */
				xlate[p] = gdImageColorClosestAlpha (from, to->red[p], to->green[p], to->blue[p], to->alpha[p]);
			}
			gdImageSetPixel(to, x, y, xlate[p]);
		}
	}

	for (i = 0; i < from->colorsTotal; i++) {
		to->red[i] = from->red[i];
		to->blue[i] = from->blue[i];
		to->green[i] = from->green[i];
		to->alpha[i] = from->alpha[i];
		to->open[i] = 0;
	}

	for (i = from->colorsTotal; i < to->colorsTotal; i++) {
		to->open[i] = 1;
	}

	to->colorsTotal = from->colorsTotal;
}

/* 2.0.10: before the drawing routines, some code to clip points that are
 * outside the drawing window.  Nick Atty ([e-mail])
 *
 * This is the Sutherland Hodgman Algorithm, as implemented by
 * Duvanenko, Robbins and Gyurcsik - SH(DRG) for short.  See Dr Dobb's
 * Journal, January 1996, pp107-110 and 116-117
 *
 * Given the end points of a line, and a bounding rectangle (which we
 * know to be from (0,0) to (SX,SY)), adjust the endpoints to be on
 * the edges of the rectangle if the line should be drawn at all,
 * otherwise return a failure code
 */

/* this does "one-dimensional" clipping: note that the second time it
 *  is called, all the x parameters refer to height and the y to width
 *  - the comments ignore this (if you can understand it when it's
 *  looking at the X parameters, it should become clear what happens on
 *  the second call!)  The code is simplified from that in the article,
 *  as we know that gd images always start at (0,0)
 */

static int clip_1d(int *x0, int *y0, int *x1, int *y1, int maxdim) {
	double m;      /* gradient of line */

	if (*x0 < 0) {  /* start of line is left of window */
		if(*x1 < 0) { /* as is the end, so the line never cuts the window */
			return 0;
		}
		m = (*y1 - *y0)/(double)(*x1 - *x0); /* calculate the slope of the line */
		/* adjust x0 to be on the left boundary (ie to be zero), and y0 to match */
		*y0 -= (int)(m * *x0);
		*x0 = 0;
		/* now, perhaps, adjust the far end of the line as well */
		if (*x1 > maxdim) {
			*y1 += (int)(m * (maxdim - *x1));
			*x1 = maxdim;
		}
		return 1;
	}
	if (*x0 > maxdim) { /* start of line is right of window - complement of above */
		if (*x1 > maxdim) { /* as is the end, so the line misses the window */
			return 0;
		}
		m = (*y1 - *y0)/(double)(*x1 - *x0);  /* calculate the slope of the line */
		*y0 += (int)(m * (maxdim - *x0)); /* adjust so point is on the right boundary */
		*x0 = maxdim;
		/* now, perhaps, adjust the end of the line */
		if (*x1 < 0) {
			*y1 -= (int)(m * *x1);
			*x1 = 0;
		}
		return 1;
	}
	/* the final case - the start of the line is inside the window */
	if (*x1 > maxdim) { /* other end is outside to the right */
		m = (*y1 - *y0)/(double)(*x1 - *x0);  /* calculate the slope of the line */
		*y1 += (int)(m * (maxdim - *x1));
		*x1 = maxdim;
		return 1;
	}
	if (*x1 < 0) { /* other end is outside to the left */
		m = (*y1 - *y0)/(double)(*x1 - *x0);  /* calculate the slope of the line */
		*y1 -= (int)(m * *x1);
		*x1 = 0;
		return 1;
	}
	/* only get here if both points are inside the window */
	return 1;
}

void gdImageSetPixel (gdImagePtr im, int x, int y, int color)
{
	int p;
	switch (color) {
		case gdStyled:
			if (!im->style) {
				/* Refuse to draw if no style is set. */
				return;
			} else {
				p = im->style[im->stylePos++];
			}
			if (p != gdTransparent) {
				gdImageSetPixel(im, x, y, p);
			}
			im->stylePos = im->stylePos % im->styleLength;
			break;
		case gdStyledBrushed:
			if (!im->style) {
				/* Refuse to draw if no style is set. */
				return;
			}
			p = im->style[im->stylePos++];
			if (p != gdTransparent && p != 0) {
				gdImageSetPixel(im, x, y, gdBrushed);
			}
			im->stylePos = im->stylePos % im->styleLength;
			break;
		case gdBrushed:
			gdImageBrushApply(im, x, y);
			break;
		case gdTiled:
			gdImageTileApply(im, x, y);
			break;
		case gdAntiAliased:
			gdImageAntiAliasedApply(im, x, y);
			break;
		default:
			if (gdImageBoundsSafe(im, x, y)) {
				if (im->trueColor) {
					switch (im->alphaBlendingFlag) {
						default:
						case gdEffectReplace:
							im->tpixels[y][x] = color;
							break;
						case gdEffectAlphaBlend:
							im->tpixels[y][x] = gdAlphaBlend(im->tpixels[y][x], color);
							break;
						case gdEffectNormal:
							im->tpixels[y][x] = gdAlphaBlend(im->tpixels[y][x], color);
							break;
						case gdEffectOverlay :
							im->tpixels[y][x] = gdLayerOverlay(im->tpixels[y][x], color);
							break;
					}
				} else {
					im->pixels[y][x] = color;
				}
			}
			break;
	}
}

int gdImageGetTrueColorPixel (gdImagePtr im, int x, int y)
{
	int p = gdImageGetPixel(im, x, y);

	if (!im->trueColor)  {
		return gdTrueColorAlpha(im->red[p], im->green[p], im->blue[p], (im->transparent == p) ? gdAlphaTransparent : gdAlphaOpaque);
	} else {
		return p;
	}
}

static void gdImageBrushApply (gdImagePtr im, int x, int y)
{
	int lx, ly;
	int hy, hx;
	int x1, y1, x2, y2;
	int srcx, srcy;

	if (!im->brush) {
		return;
	}

	hy = gdImageSY(im->brush) / 2;
	y1 = y - hy;
	y2 = y1 + gdImageSY(im->brush);
	hx = gdImageSX(im->brush) / 2;
	x1 = x - hx;
	x2 = x1 + gdImageSX(im->brush);
	srcy = 0;

	if (im->trueColor) {
		if (im->brush->trueColor) {
			for (ly = y1; ly < y2; ly++) {
				srcx = 0;
				for (lx = x1; (lx < x2); lx++) {
					int p;
					p = gdImageGetTrueColorPixel(im->brush, srcx, srcy);
					/* 2.0.9, Thomas Winzig: apply simple full transparency */
					if (p != gdImageGetTransparent(im->brush)) {
						gdImageSetPixel(im, lx, ly, p);
					}
					srcx++;
				}
				srcy++;
			}
		} else {
			/* 2.0.12: Brush palette, image truecolor (thanks to Thorben Kundinger for pointing out the issue) */
			for (ly = y1; ly < y2; ly++) {
				srcx = 0;
				for (lx = x1; lx < x2; lx++) {
					int p, tc;
					p = gdImageGetPixel(im->brush, srcx, srcy);
					tc = gdImageGetTrueColorPixel(im->brush, srcx, srcy);
					/* 2.0.9, Thomas Winzig: apply simple full transparency */
					if (p != gdImageGetTransparent(im->brush)) {
						gdImageSetPixel(im, lx, ly, tc);
					}
					srcx++;
				}
				srcy++;
			}
		}
	} else {
		for (ly = y1; ly < y2; ly++) {
			srcx = 0;
			for (lx = x1; lx < x2; lx++) {
				int p;
				p = gdImageGetPixel(im->brush, srcx, srcy);
				/* Allow for non-square brushes! */
				if (p != gdImageGetTransparent(im->brush)) {
					/* Truecolor brush. Very slow on a palette destination. */
					if (im->brush->trueColor) {
						gdImageSetPixel(im, lx, ly, gdImageColorResolveAlpha(im, gdTrueColorGetRed(p),
													 gdTrueColorGetGreen(p),
													 gdTrueColorGetBlue(p),
													 gdTrueColorGetAlpha(p)));
					} else {
						gdImageSetPixel(im, lx, ly, im->brushColorMap[p]);
					}
				}
				srcx++;
			}
			srcy++;
		}
	}
}

static void gdImageTileApply (gdImagePtr im, int x, int y)
{
	int srcx, srcy;
	int p;
	if (!im->tile) {
		return;
	}
	srcx = x % gdImageSX(im->tile);
	srcy = y % gdImageSY(im->tile);
	if (im->trueColor) {
		p = gdImageGetTrueColorPixel(im->tile, srcx, srcy);
		gdImageSetPixel(im, x, y, p);
	} else {
		p = gdImageGetPixel(im->tile, srcx, srcy);
		/* Allow for transparency */
		if (p != gdImageGetTransparent(im->tile)) {
			if (im->tile->trueColor) {
				/* Truecolor tile. Very slow on a palette destination. */
				gdImageSetPixel(im, x, y, gdImageColorResolveAlpha(im,
											gdTrueColorGetRed(p),
											gdTrueColorGetGreen(p),
											gdTrueColorGetBlue(p),
											gdTrueColorGetAlpha(p)));
			} else {
				gdImageSetPixel(im, x, y, im->tileColorMap[p]);
			}
		}
	}
}


static int gdImageTileGet (gdImagePtr im, int x, int y)
{
	int srcx, srcy;
	int tileColor,p;
	if (!im->tile) {
		return -1;
	}
	srcx = x % gdImageSX(im->tile);
	srcy = y % gdImageSY(im->tile);
	p = gdImageGetPixel(im->tile, srcx, srcy);

	if (im->trueColor) {
		if (im->tile->trueColor) {
			tileColor = p;
		} else {
			tileColor = gdTrueColorAlpha( gdImageRed(im->tile,p), gdImageGreen(im->tile,p), gdImageBlue (im->tile,p), gdImageAlpha (im->tile,p));
		}
	} else {
		if (im->tile->trueColor) {
			tileColor = gdImageColorResolveAlpha(im, gdTrueColorGetRed (p), gdTrueColorGetGreen (p), gdTrueColorGetBlue (p), gdTrueColorGetAlpha (p));
		} else {
			tileColor = p;
			tileColor = gdImageColorResolveAlpha(im, gdImageRed (im->tile,p), gdImageGreen (im->tile,p), gdImageBlue (im->tile,p), gdImageAlpha (im->tile,p));
		}
	}
	return tileColor;
}


static void gdImageAntiAliasedApply (gdImagePtr im, int px, int py)
{
	float p_dist, p_alpha;
	unsigned char opacity;

	/*
	 * Find the perpendicular distance from point C (px, py) to the line
	 * segment AB that is being drawn.  (Adapted from an algorithm from the
	 * comp.graphics.algorithms FAQ.)
	 */

	int LAC_2, LBC_2;

	int Ax_Cx = im->AAL_x1 - px;
	int Ay_Cy = im->AAL_y1 - py;

	int Bx_Cx = im->AAL_x2 - px;
	int By_Cy = im->AAL_y2 - py;

	/* 2.0.13: bounds check! AA_opacity is just as capable of
	 * overflowing as the main pixel array. Arne Jorgensen.
	 * 2.0.14: typo fixed. 2.0.15: moved down below declarations
	 * to satisfy non-C++ compilers.
	 */
	if (!gdImageBoundsSafe(im, px, py)) {
		return;
	}

	/* Get the squares of the lengths of the segemnts AC and BC. */
	LAC_2 = (Ax_Cx * Ax_Cx) + (Ay_Cy * Ay_Cy);
	LBC_2 = (Bx_Cx * Bx_Cx) + (By_Cy * By_Cy);

	if (((im->AAL_LAB_2 + LAC_2) >= LBC_2) && ((im->AAL_LAB_2 + LBC_2) >= LAC_2)) {
		/* The two angles are acute.  The point lies inside the portion of the
		 * plane spanned by the line segment.
		 */
		p_dist = fabs ((float) ((Ay_Cy * im->AAL_Bx_Ax) - (Ax_Cx * im->AAL_By_Ay)) / im->AAL_LAB);
	} else {
		/* The point is past an end of the line segment.  It's length from the
		 * segment is the shorter of the lengths from the endpoints, but call
		 * the distance -1, so as not to compute the alpha nor draw the pixel.
		 */
		p_dist = -1;
	}

	if ((p_dist >= 0) && (p_dist <= (float) (im->thick))) {
		p_alpha = pow (1.0 - (p_dist / 1.5), 2);

		if (p_alpha > 0) {
			if (p_alpha >= 1) {
				opacity = 255;
			} else {
				opacity = (unsigned char) (p_alpha * 255.0);
			}
			if (!im->AA_polygon || (im->AA_opacity[py][px] < opacity)) {
				im->AA_opacity[py][px] = opacity;
			}
		}
	}
}


int gdImageGetPixel (gdImagePtr im, int x, int y)
{
	if (gdImageBoundsSafe(im, x, y)) {
		if (im->trueColor) {
			return im->tpixels[y][x];
		} else {
			return im->pixels[y][x];
		}
	} else {
		return 0;
	}
}

void gdImageAABlend (gdImagePtr im)
{
	float p_alpha, old_alpha;
	int color = im->AA_color, color_red, color_green, color_blue;
	int old_color, old_red, old_green, old_blue;
	int p_color, p_red, p_green, p_blue;
	int px, py;

	color_red = gdImageRed(im, color);
	color_green = gdImageGreen(im, color);
	color_blue = gdImageBlue(im, color);

	/* Impose the anti-aliased drawing on the image. */
	for (py = 0; py < im->sy; py++) {
		for (px = 0; px < im->sx; px++) {
			if (im->AA_opacity[py][px] != 0) {
				old_color = gdImageGetPixel(im, px, py);

				if ((old_color != color) && ((old_color != im->AA_dont_blend) || (im->AA_opacity[py][px] == 255))) {
					/* Only blend with different colors that aren't the dont_blend color. */
					p_alpha = (float) (im->AA_opacity[py][px]) / 255.0;
					old_alpha = 1.0 - p_alpha;

					if (p_alpha >= 1.0) {
						p_color = color;
					} else {
						old_red = gdImageRed(im, old_color);
						old_green = gdImageGreen(im, old_color);
						old_blue = gdImageBlue(im, old_color);

						p_red = (int) (((float) color_red * p_alpha) + ((float) old_red * old_alpha));
						p_green = (int) (((float) color_green * p_alpha) + ((float) old_green * old_alpha));
						p_blue = (int) (((float) color_blue * p_alpha) + ((float) old_blue * old_alpha));
						p_color = gdImageColorResolve(im, p_red, p_green, p_blue);
					}
					gdImageSetPixel(im, px, py, p_color);
				}
			}
		}
		/* Clear the AA_opacity array behind us. */
		memset(im->AA_opacity[py], 0, im->sx);
	}
}


/* Bresenham as presented in Foley & Van Dam */
void gdImageLine (gdImagePtr im, int x1, int y1, int x2, int y2, int color)
{
	int t;
	int dx, dy, incr1, incr2, d, x, y, xend, yend, xdirflag, ydirflag;
	int wid;
	int w, wstart;
	int thick = im->thick;

	/* 2.0.10: Nick Atty: clip to edges of drawing rectangle, return if no points need to be drawn */
	if (!clip_1d(&x1,&y1,&x2,&y2,gdImageSX(im)) || !clip_1d(&y1,&x1,&y2,&x2,gdImageSY(im))) {
		return;
	}

	/* Vertical */
	if (x1==x2) {
		if (y2 < y1) {
			t = y2;
			y2 = y1;
			y1 = t;
		}

		for (;y1 <= y2; y1++) {
			gdImageSetPixel(im, x1,y1, color);
		}
		return;
	}

	/* Horizontal */
	if (y1==y2) {
		if (x2 < x1) {
			t = x2;
			x2 = x1;
			x1 = t;
		}

		for (;x1 <= x2; x1++) {
			gdImageSetPixel(im, x1,y1, color);
		}
		return;
	}

	/* gdAntiAliased passed as color: set anti-aliased line (AAL) global vars. */
	if (color == gdAntiAliased) {
		im->AAL_x1 = x1;
		im->AAL_y1 = y1;
		im->AAL_x2 = x2;
		im->AAL_y2 = y2;

		/* Compute what we can for point-to-line distance calculation later. */
		im->AAL_Bx_Ax = x2 - x1;
		im->AAL_By_Ay = y2 - y1;
		im->AAL_LAB_2 = (im->AAL_Bx_Ax * im->AAL_Bx_Ax) + (im->AAL_By_Ay * im->AAL_By_Ay);
		im->AAL_LAB = sqrt (im->AAL_LAB_2);

		/* For AA, we must draw pixels outside the width of the line.  Keep in
		 * mind that this will be curtailed by cos/sin of theta later.
		 */
		thick += 4;
	}

	dx = abs(x2 - x1);
	dy = abs(y2 - y1);
	if (dy <= dx) {
		/* More-or-less horizontal. use wid for vertical stroke */
		/* Doug Claar: watch out for NaN in atan2 (2.0.5) */
		if ((dx == 0) && (dy == 0)) {
			wid = 1;