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e7ce6468fcaf977aa52a0c76ba654faa8fcc3ed3
wmaker/wrlib/draw.c
dan e7ce6468fc - fixed code in wrlib dependant on the order of evaluation. 
code like
    *ptr++ = *ptr++ = *ptr++ = color;
  is wrong, because there is no guarantee that ptr will be incremented
  _between_ the assignment operations. it can be incremented after all
  assignment operations as well. Because of this both of these are valid
  implementations for a compiler:
    a. assign, increment, assign, increment, assign, increment
    b. assign, assign, assign, increment by 3
  In case b. only the first memory location of the 3 will be modified, being
  assigned 3 times the same value, while the other 2 remain unchanged.
  For example egcs-2.91.66 (and possibly gcc-2.95.x too) implement this in
  the second way (like in case b.)
  Also the order in which the assignement is made is undefined (left to right
  or right to left).

this fixed the problem we had with greyscale jpegs showing up in red,
and possibly other problems related to pseudocolor and greyscale displays.
2000-11-06 04:21:25 +00:00

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/* draw.c - pixel plotting, line drawing
*
* Raster graphics library
*
* Copyright (c) 1998 Dan Pascu
* Copyright (c) 2000 Alfredo K. Kojima
*
* 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;
if (image->format == RRGBAFormat) {
ofs = (y*image->width + x) * 4;
color->red = image->data[ofs];
color->green = image->data[ofs++];
color->blue = image->data[ofs++];
color->alpha = image->data[ofs];
} else {
ofs = (y*image->width + x) * 3;
color->red = image->data[ofs++];
color->green = image->data[ofs++];
color->blue = image->data[ofs++];
/* If the image does not have alpha channel, we consider alpha 255 */
color->alpha = 255;
}
return True;
}
void
RPutPixel(RImage *image, int x, int y, RColor *color)
{
unsigned char *ptr;
assert(image!=NULL);
assert(color!=NULL);
if (x < 0 || x >= image->width || y < 0 || y >= image->height)
return;
if (image->format == RRGBAFormat) {
ptr = image->data + (y*image->width + x) * 4;
} else {
ptr = image->data + (y*image->width + x) * 3;
}
if (color->alpha==255) {
*ptr++ = color->red;
*ptr++ = color->green;
*ptr++ = color->blue;
if (image->format == RRGBAFormat) {
*ptr = 255;
}
} else {
register int alpha, nalpha, r, g, b;
r = color->red;
g = color->green;
b = color->blue;
alpha = color->alpha;
nalpha = 255 - alpha;
*ptr = (((int)*ptr * nalpha) + (r * alpha))/256; ptr++;
*ptr = (((int)*ptr * nalpha) + (g * alpha))/256; ptr++;
*ptr = (((int)*ptr * nalpha) + (b * alpha))/256; ptr++;
if (image->format == RRGBAFormat) {
*ptr = alpha + ((int)*ptr * 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->format == RRGBAFormat;
alpha = color->alpha;
nalpha = 255 - alpha;
sr = image->data + ofs*(hasAlpha ? 4 : 3);
sg = image->data + ofs*(hasAlpha ? 4 : 3) + 1;
sb = image->data + ofs*(hasAlpha ? 4 : 3) + 2;
sa = image->data + ofs*(hasAlpha ? 4 : 3) + 3;
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);
}
}
static Bool
clipLineInRectangle(int xmin, int ymin, int xmax, int ymax,
int *x1, int *y1, int *x2, int *y2)
{
#define TOP (1<<0)
#define BOT (1<<1)
#define LEF (1<<2)
#define RIG (1<<3)
#define CHECK_OUT(X,Y) (((Y) > ymax ? TOP : ((Y) < ymin ? BOT : 0))\
| ((X) > xmax ? RIG : ((X) < xmin ? LEF : 0)))
int ocode1, ocode2, ocode;
int accept = 0;
int x, y;
ocode1 = CHECK_OUT(*x1, *y1);
ocode2 = CHECK_OUT(*x2, *y2);
for(;;) {
if (!ocode1 && !ocode2) { /* completely inside */
accept = 1;
break;
} else if (ocode1 & ocode2) {
break;
}
if (ocode1)
ocode = ocode1;
else
ocode = ocode2;
if (ocode & TOP) {
x = *x1 + (*x2 - *x1) * (ymax - *y1) / (*y2 - *y1);
y = ymax;
} else if (ocode & BOT) {
x = *x1 + (*x2 - *x1) * (ymin - *y1) / (*y2 - *y1);
y = ymin;
} else if (ocode & RIG) {
y = *y1 + (*y2 - *y1) * (xmax - *x1) / (*x2 - *x1);
x = xmax;
} else if (ocode & LEF) {
y = *y1 + (*y2 - *y1) * (xmax - *x1) / (*x2 - *x1);
x = xmin;
}
if (ocode == ocode1) {
*x1 = x;
*y1 = y;
ocode1 = CHECK_OUT(x, y);
} else {
*x2 = x;
*y2 = y;
ocode2 = CHECK_OUT(x, y);
}
}
return accept;
}
/*
* 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);
if (!clipLineInRectangle(0, 0, image->width-1, image->height-1,
&x0, &y0, &x1, &y1))
return True;
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 *ptr;
if (image->format == RRGBAFormat)
i = (y0*image->width + x0) * 4;
else
i = (y0*image->width + x0) * 3;
ptr = image->data + i;
for (i=0; i<=last; i++) {
/* Draw the pixel */
*ptr = color->red;
*(ptr+1) = color->green;
*(ptr+2) = color->blue;
if (image->format == RRGBAFormat)
*(ptr+3) = 255;
/* Compute error for NeXT Step */
err += dv2;
if (err >= du) {
if (image->format == RRGBAFormat)
ptr += vofs*4;
else
ptr += vofs*3;
err -= du2;
}
if (image->format == RRGBAFormat)
ptr += uofs*4;
else
ptr += uofs*3;
}
} 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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