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wmaker/wrlib/draw.c
scottc 9d2e6ef9f1 Initial revision
1998-09-29 22:36:29 +00:00

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/* draw.c - pixel plotting, line drawing
*
* Raster graphics library
*
* Copyright (c) 1998 Dan Pascu
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "wraster.h"
#define MIN(a,b) ((a) < (b) ? (a) : (b))
#define MAX(a,b) ((a) > (b) ? (a) : (b))
/*
* Returns the color of the pixel at coordinates (x, y) in "color".
*/
Bool
RGetPixel(RImage *image, int x, int y, RColor *color)
{
int ofs;
assert(image!=NULL);
if (x < 0 || x >= image->width
|| y < 0 || y >= image->height)
return False;
ofs = y*image->width + x;
color->red = image->data[0][ofs];
color->green = image->data[1][ofs];
color->blue = image->data[2][ofs];
/* If the image does not have alpha channel, we consider alpha 255 */
if (image->data[3])
color->alpha = image->data[3][ofs];
else
color->alpha = 255;
return True;
}
void
RPutPixel(RImage *image, int x, int y, RColor *color)
{
int ofs;
unsigned char *sr, *sg, *sb, *sa;
assert(image!=NULL);
assert(color!=NULL);
assert(x >= 0 && x < image->width);
assert(y >= 0 && y < image->height);
ofs = y*image->width + x;
sr = image->data[0] + ofs;
sg = image->data[1] + ofs;
sb = image->data[2] + ofs;
sa = image->data[3] + ofs;
if (color->alpha==255) {
*sr = color->red;
*sg = color->green;
*sb = color->blue;
if (image->data[3])
*sa = 255;
} else {
register int alpha, nalpha, r, g, b;
r = color->red;
g = color->green;
b = color->blue;
alpha = color->alpha;
nalpha = 255 - alpha;
*sr = (((int)*sr * nalpha) + (r * alpha))/256;
*sg = (((int)*sg * nalpha) + (g * alpha))/256;
*sb = (((int)*sb * nalpha) + (b * alpha))/256;
if (image->data[3])
*sa = alpha + ((int)*sa * nalpha)/256;
}
}
static void
operatePixel(RImage *image, int ofs, int operation, RColor *color)
{
unsigned char *sr, *sg, *sb, *sa;
register int alpha, nalpha, tmp;
int hasAlpha = image->data[3]!=NULL;
alpha = color->alpha;
nalpha = 255 - alpha;
sr = image->data[0] + ofs;
sg = image->data[1] + ofs;
sb = image->data[2] + ofs;
sa = image->data[3] + ofs;
switch (operation) {
case RClearOperation:
*sr = 0;
*sg = 0;
*sb = 0;
if (hasAlpha)
*sa = 0;
break;
case RCopyOperation:
*sr = color->red;
*sg = color->green;
*sb = color->blue;
if (hasAlpha)
*sa = color->alpha;
break;
case RNormalOperation:
if (color->alpha==255) {
*sr = color->red;
*sg = color->green;
*sb = color->blue;
if (hasAlpha)
*sa = 255;
} else {
*sr = (((int)*sr * nalpha) + ((int)color->red * alpha))/256;
*sg = (((int)*sg * nalpha) + ((int)color->green * alpha))/256;
*sb = (((int)*sb * nalpha) + ((int)color->blue * alpha))/256;
}
break;
case RAddOperation:
tmp = color->red + *sr;
*sr = MIN(255, tmp);
tmp = color->green + *sg;
*sg = MIN(255, tmp);
tmp = color->blue + *sb;
*sb = MIN(255, tmp);
if (hasAlpha)
*sa = MIN(*sa, color->alpha);
break;
case RSubtractOperation:
tmp = *sr - color->red;
*sr = MAX(0, tmp);
tmp = *sg - color->green;
*sg = MAX(0, tmp);
tmp = *sb - color->blue;
*sb = MAX(0, tmp);
if (hasAlpha)
*sa = MIN(*sa, color->alpha);
break;
}
}
void
ROperatePixel(RImage *image, int operation, int x, int y, RColor *color)
{
int ofs;
assert(image!=NULL);
assert(color!=NULL);
assert(x >= 0 && x < image->width);
assert(y >= 0 && y < image->height);
ofs = y*image->width + x;
operatePixel(image, ofs, operation, color);
}
void
RPutPixels(RImage *image, RPoint *points, int npoints, int mode, RColor *color)
{
register int x, y, i;
assert(image!=NULL);
assert(points!=NULL);
x = y = 0;
for (i=0; i<npoints; i++) {
if (mode == RAbsoluteCoordinates) {
x = points[i].x;
y = points[i].y;
} else {
x += points[i].x;
y += points[i].y;
}
RPutPixel(image, x, y, color);
}
}
void
ROperatePixels(RImage *image, int operation, RPoint *points, int npoints,
int mode, RColor *color)
{
register int x, y, i;
assert(image!=NULL);
assert(points!=NULL);
x = y = 0;
for (i=0; i<npoints; i++) {
if (mode == RAbsoluteCoordinates) {
x = points[i].x;
y = points[i].y;
} else {
x += points[i].x;
y += points[i].y;
}
ROperatePixel(image, operation, x, y, color);
}
}
/*
* This routine is a generic drawing routine, based on Bresenham's line
* drawing algorithm.
*/
static int
genericLine(RImage *image, int x0, int y0, int x1, int y1, RColor *color,
int operation, int polyline)
{
int i, err, du, dv, du2, dv2, uofs, vofs, last;
assert(image!=NULL);
assert(x0 >= 0 && x0 <= image->width);
assert(x1 >= 0 && x1 <= image->width);
assert(y0 >= 0 && y0 <= image->height);
assert(y1 >= 0 && y1 <= image->height);
if (x0 < x1) {
du = x1 - x0;
uofs = 1;
} else {
du = x0 - x1;
uofs = -1;
}
if (y0 < y1) {
dv = y1 -y0;
vofs = image->width;
} else {
dv = y0 - y1;
vofs = -image->width;
}
if (du < dv) {
/* Swap coordinates between them, so that always du>dv */
i = du; du = dv; dv = i;
i = uofs; uofs = vofs; vofs = i;
}
err = 0;
du2 = du<<1;
dv2 = dv<<1;
last = (polyline) ? du-1 : du;
if (color->alpha==255 || operation==RCopyOperation) {
unsigned char *sr, *sg, *sb, *sa;
i = y0*image->width + x0;
sr = image->data[0] + i;
sg = image->data[1] + i;
sb = image->data[2] + i;
sa = image->data[3] + i;
for (i=0; i<=last; i++) {
/* Draw the pixel */
*sr = color->red;
*sg = color->green;
*sb = color->blue;
if (image->data[3])
*sa = 255;
/* Compute error for NeXT Step */
err += dv2;
if (err >= du) {
sr += vofs; sg += vofs;
sb += vofs; sa += vofs;
err -= du2;
}
sr += uofs; sg += uofs;
sb += uofs; sa += uofs;
}
} else {
register int ofs = y0*image->width + x0;
for (i=0; i<=last; i++) {
/* Draw the pixel */
operatePixel(image, ofs, operation, color);
/* Compute error for NeXT Step */
err += dv2;
if (err >= du) {
ofs += vofs;
err -= du2;
}
ofs += uofs;
}
}
#if 0
if (mode == RALTER_PIXELS) {
RColorOffset *cdelta = (RColorOffset*)cdata;
register short r, g, b, a;
for (i=0; i<=last; i++) {
/* Change the pixel with offset */
r = (short)*sr + cdelta->red;
g = (short)*sg + cdelta->green;
b = (short)*sb + cdelta->blue;
if (r>255) r = 255; else if (r<0) r = 0;
if (g>255) g = 255; else if (g<0) g = 0;
if (b>255) b = 255; else if (b<0) b = 0;
*sr = (unsigned char) r;
*sg = (unsigned char) g;
*sb = (unsigned char) b;
if (image->data[3]) {
a = (short)*sa + cdelta->alpha;
if (a>255) a = 255; else if (a<0) a = 0;
*sa = (unsigned char) a;
}
/* Compute error for NeXT Step */
err += dv2;
if (err >= du) {
sr += vofs; sg += vofs;
sb += vofs; sa += vofs;
err -= du2;
}
sr += uofs; sg += uofs;
sb += uofs; sa += uofs;
}
} else {
RColor *color = (RColor*)cdata;
if (color->alpha==255) {
for (i=0; i<=last; i++) {
/* Draw the pixel */
*sr = color->red;
*sg = color->green;
*sb = color->blue;
if (image->data[3])
*sa = 255;
/* Compute error for NeXT Step */
err += dv2;
if (err >= du) {
sr += vofs; sg += vofs;
sb += vofs; sa += vofs;
err -= du2;
}
sr += uofs; sg += uofs;
sb += uofs; sa += uofs;
}
} else {
register short alpha, nalpha, r, g ,b;
alpha = color->alpha;
nalpha = 255 - alpha;
r = color->red;
g = color->green;
b = color->blue;
for (i=0; i<=last; i++) {
/* Draw the pixel */
*sr = (((int)*sr * nalpha) + (r * alpha))/256;
*sg = (((int)*sg * nalpha) + (g * alpha))/256;
*sb = (((int)*sb * nalpha) + (b * alpha))/256;
if (image->data[3])
*sa = alpha + ((int)*sa * nalpha)/256;
/* Compute error for NeXT Step */
err += dv2;
if (err >= du) {
sr += vofs; sg += vofs;
sb += vofs; sa += vofs;
err -= du2;
}
sr += uofs; sg += uofs;
sb += uofs; sa += uofs;
}
}
}
#endif
return True;
}
int
RDrawLine(RImage *image, int x0, int y0, int x1, int y1, RColor *color)
{
return genericLine(image, x0, y0, x1, y1, color, RNormalOperation, False);
}
int
ROperateLine(RImage *image, int operation, int x0, int y0, int x1,
int y1, RColor *color)
{
return genericLine(image, x0, y0, x1, y1, color, operation, False);
}
void
RDrawLines(RImage *image, RPoint *points, int npoints, int mode, RColor *color)
{
register int x1, y1, x2, y2, i;
assert(points!=NULL);
if (npoints==0)
return;
x1 = points[0].x;
y1 = points[0].y;
x2 = y2 = 0;
for (i=1; i<npoints-1; i++) {
if (mode == RAbsoluteCoordinates) {
x2 = points[i].x;
y2 = points[i].y;
} else {
x2 += points[i-1].x;
y2 += points[i-1].y;
}
/* Don't draw pixels at junction points twice */
genericLine(image, x1, y1, x2, y2, color, RNormalOperation, True);
x1 = x2;
y1 = y2;
}
i = npoints-1; /* last point */
if (mode == RAbsoluteCoordinates) {
x2 = points[i].x;
y2 = points[i].y;
} else {
x2 += points[i-1].x;
y2 += points[i-1].y;
}
i = (points[0].x==x2 && points[0].y==y2 && npoints>1);
genericLine(image, x1, y1, x2, y2, color, RNormalOperation, i);
}
void
ROperateLines(RImage *image, int operation, RPoint *points,
int npoints, int mode, RColor *color)
{
register int x1, y1, x2, y2, i;
assert(points!=NULL);
if (npoints==0)
return;
x1 = points[0].x;
y1 = points[0].y;
x2 = y2 = 0;
for (i=1; i<npoints-1; i++) {
if (mode == RAbsoluteCoordinates) {
x2 = points[i].x;
y2 = points[i].y;
} else {
x2 += points[i-1].x;
y2 += points[i-1].y;
}
/* Don't draw pixels at junction points twice */
genericLine(image, x1, y1, x2, y2, color, operation, True);
x1 = x2;
y1 = y2;
}
i = npoints-1; /* last point */
if (mode == RAbsoluteCoordinates) {
x2 = points[i].x;
y2 = points[i].y;
} else {
x2 += points[i-1].x;
y2 += points[i-1].y;
}
i = (points[0].x==x2 && points[0].y==y2 && npoints>1);
genericLine(image, x1, y1, x2, y2, color, operation, i);
}
void
RDrawSegments(RImage *image, RSegment *segs, int nsegs, RColor *color)
{
register int i;
assert(segs!=NULL);
for (i=0; i<nsegs; i++) {
genericLine(image, segs->x1, segs->y1, segs->x2, segs->y2, color,
RNormalOperation, False);
segs++;
}
}
void
ROperateSegments(RImage *image, int operation, RSegment *segs,
int nsegs, RColor *color)
{
register int i;
assert(segs!=NULL);
for (i=0; i<nsegs; i++) {
genericLine(image, segs->x1, segs->y1, segs->x2, segs->y2, color,
operation, False);
segs++;
}
}
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