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A unidirectional error-spread makes the saddest little thumbnails taste 

Sun Feb  7 18:29:26 GMT 1999 Adam D. Moss <adam@gimp.org>

	* app/fileops.c: A unidirectional error-spread makes
	the saddest little thumbnails taste full of country
	goodness.

	* app/appenv.c: Wow, CLAMP0255() has a bug that I can't
	quite see, or my compiler does.  Worked around it.
This commit is contained in:
GMT 1999 Adam D. Moss 1999-02-07 18:34:16 +00:00 committed by Adam D. Moss
parent 32675c4408
commit 0fe096b299
3 changed files with 48 additions and 12 deletions
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9
ChangeLog
View File

@ -1,3 +1,12 @@
Sun Feb 7 18:29:26 GMT 1999 Adam D. Moss <adam@gimp.org>
* app/fileops.c: A unidirectional error-spread makes
the saddest little thumbnails taste full of country
goodness.
* app/appenv.c: Wow, CLAMP0255() has a bug that I can't
quite see, or my compiler does. Worked around it.
Sun Feb 7 15:04:23 GMT 1999 Adam D. Moss <adam@gimp.org>
* app/fileops.c: More robust and kickin' thumbnail support.

5
app/appenv.h
View File

@ -33,8 +33,9 @@
/* limit a (0->511) int to 255 */
#define MAX255(a) (a | ((a & 256) - ((a & 256) >> 8)))
/* clamp a int32-range int between 0 and 255 inclusive */
#define CLAMP0255(a) ((a&256)? (~(a>>31)) : a)
/* clamp a >>int32<<-range int between 0 and 255 inclusive */
/* broken! -> #define CLAMP0255(a) ((a & 0xFFFFFF00)? (~(a>>31)) : a) */
#define CLAMP0255(a) CLAMP(a,0,255)
typedef enum {

46
app/fileops.c
View File

@ -983,28 +983,54 @@ file_save_thumbnail (GimpImage* gimage,
{
case INDEXED:
case RGB:
for (i=0;i<w;i++)
for (i=0; i<h; i++)
{
for (j=0;j<h;j++)
/* Do a cheap unidirectional error-spread to look better */
gint rerr=0, gerr=0, berr=0;
for (j=0; j<w; j++)
{
guchar r,g,b;
r = *(tbd++);
g = *(tbd++);
b = *(tbd++);
gint32 r,g,b;
r = *(tbd++) + rerr;
g = *(tbd++) + gerr;
b = *(tbd++) + berr;
tbd++;
r = CLAMP0255 (r);
g = CLAMP0255 (g);
b = CLAMP0255 (b);
fputc(((r>>5)<<5) | ((g>>5)<<2) | (b>>6), fp);
rerr = r - ( (r>>5) * 255 ) / 7;
gerr = g - ( (g>>5) * 255 ) / 7;
berr = b - ( (b>>6) * 255 ) / 3;
}
}
break;
case GRAY:
for (i=0;i<w;i++)
for (i=0; i<h; i++)
{
for (j=0;j<h;j++)
/* Do a cheap unidirectional error-spread to look better */
gint b3err=0, b2err=0, v;
for (j=0; j<w; j++)
{
guchar v;
gint32 b3, b2;
v = *(tbd++);
tbd++;
fputc(((v>>5)<<5) | ((v>>5)<<2) | (v>>6), fp);
b2 = v + b2err;
b3 = v + b3err;
b2 = CLAMP0255 (b2);
b3 = CLAMP0255 (b3);
fputc(((b3>>5)<<5) | ((b3>>5)<<2) | (b2>>6), fp);
b2err = b2 - ( (b2>>6) * 255 ) / 3;
b3err = b3 - ( (b3>>5) * 255 ) / 7;
}
}
break;