ceti (ceti++at++worldnet.net)
Wed, 26 Feb 1997 12:53:58 +0000
when you insert sgi image file, showcase asks you if you want to use or discard
alpha channel: use it.
If showcase does the import directly, there is no alpha on your image.
then insert the second one.
If you put image 2 on image 1 then you'll see 1 trought 2.
if you need 2 throught 1, just push image 2 to the bottom of the stack.
Take care, when using imgworks, it adds a full opaque alpha bitplane, even
if the image had none before.
Now if you need to change this alpha, I can give you a C code that mix RGB
and a RGB black and white to create a RGBA image.
I use the color to greyscale option of imgworks to generate the B&W image.
The mask is taken in the first color buffer, so if it is .bw or .int it is
ok, if it is .rgb or .rgba, just the red buffer is taken as mask.
/*
* addalpha - Read RGB and RGB colored to grey scale images files
* to create a RGBA
*
* To compile: cc addalpha.c -o addalpha -limage
*
* BILLARD Olivier C&I Software
*
* parts from : SGI - Paul Haeberli - 1991
*/
#include <gl/image.h>
main(argc,argv)
int argc;
char **argv;
{
IMAGE *imagergb;
IMAGE *imagea;
IMAGE *imagergba;
int x, y, z;
short *rbuf, *gbuf, *bbuf,*abuf;
/* print usage message */
if( argc<4 )
{
fprintf(stderr,"usage: addalpha rgbinfile alphainfile outfile\n");
exit(1);
}
/* open the image file */
if( (imagergb=iopen(argv[1],"r")) == NULL )
{
fprintf(stderr,"addalpha: can't open input file %s\n",argv[1]);
exit(1);
}
if( (imagea=iopen(argv[2],"r")) == NULL )
{
fprintf(stderr,"addalpha: can't open input file %s\n",argv[2]);
exit(1);
}
if(
(imagergba=iopen(argv[3],"w",RLE(1),3,imagergb->xsize,imagergb->ysize,4)) ==
NULL )
{
fprintf(stderr,"addalpha: can't open input file %s\n",argv[3]);
exit(1);
}
/* print a little info about the image */
printf("Image x and y size in pixels: %d %d\n",imagergb->xsize,imagergb->ysize);
printf("Image zsize in channels: %d\n",imagergb->zsize);
printf("Image pixel min and max: %d %d\n",imagergb->min,imagergb->max);
/* allocate buffers for image data */
rbuf = (short *)malloc(imagergb->xsize*sizeof(short));
gbuf = (short *)malloc(imagergb->xsize*sizeof(short));
bbuf = (short *)malloc(imagergb->xsize*sizeof(short));
abuf = (short *)malloc(imagergb->xsize*sizeof(short));
imagergba->zsize >= 4;
for(y=0; y<imagergb->ysize; y++)
{
printf("row %d: \n",y);
getrow(imagergb,rbuf,y,0);
getrow(imagergb,gbuf,y,1);
getrow(imagergb,bbuf,y,2);
getrow(imagea,abuf,y,0);
putrow(imagergba,rbuf,y,0);
putrow(imagergba,gbuf,y,1);
putrow(imagergba,bbuf,y,2);
putrow(imagergba,abuf,y,3);
}
iclose(imagergb);
iclose(imagea);
iclose(imagergba);
printf("done\n");
}
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BILLARD Olivier - Engineer R&D - C&I Software
1 avenue de la mer - 44380 PORNICHET - FRANCE
Tel: +33 2 40 11 68 72 Fax: +33 2 40 61 68 14
Email: ceti++at++worldnet.net URL:http://www.worldnet.net/~ceti
=================================================================
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+----------------oOOo-(_)-oOOo----------------------+
| " We don't inherit the world from our ancestors, |
| it's only a loan from our children ." |
| Antoine de Saint Exupery. |
+-------------------------Oooo----------------------+
oooO ( )
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