Hi,
On 10:06, Thu 15 May 08, Sven Neumann wrote:
> Changing this in GIMP is not feasible. What needs to be done is to
> implement shortcuts for the conversions that GIMP actually uses.
> Eventually he gimp-8bit extension should provide shortcuts for both
> gamma-corrected and linear 8bit <-> double conversions.
attached is a patch that adds RGBA float->RGB u8 conversion
using code already present in gggl-lies extension based on
lookup table. I can try to move the code to the gimp-8bit
extension, although I don't think there is a point to doing
so, since this would only introduce duplicity and whould
increase memory footprint of BABL. However, for this
conversion to be selected, BABL_ERROR must be set at
least to 0.0005.
> The lookup tables in gegl-fixups are rather large, btw. As pointed out
> in the paper, a much smaller lookup table would be sufficient to cover
> the range from 0.0 to 1.0. I guess that adding a clever range check and
> reducing the size of the lookup tables would yield a performance
> improvement due to better cache coherency.
The lookup tables for float->u8 conversions are rather quite
large and it is indeed possible to add a range check to size
them down. However this range check would have to be
present in the inner loop of a conversion, which would
rather slow things down. Further, it wouldn't IMHO improve cache
coherency much, since the pixels already are in the 0-1 range
most of the time meaning only approx. 2.5% of the lookup
table items are frequently touched.
Regards,
Jan
Index: extensions/gggl-lies.c
===================================================================
--- extensions/gggl-lies.c (revision 311)
+++ extensions/gggl-lies.c (working copy)
@@ -62,13 +62,17 @@ static float table_16_F[1 << 16
static unsigned char table_F_8[1 << 16];
static unsigned short table_F_16[1 << 16];
-
static int table_inited = 0;
static void
table_init (void)
{
int i;
+ union
+ {
+ float f;
+ unsigned short s[2];
+ } u;
if (table_inited)
return;
@@ -84,64 +88,48 @@ table_init (void)
table_16_F[i] = (i * 1.0) / 65535.0;
}
/* fill tables for conversion from float to integer */
- {
- union
+
+ u.s[0] = 0;
+ for (i = 0; i < 1 << 16; i++)
{
- float f;
- unsigned short s[2];
- } u;
- u.f = 0.0;
-
- u.s[0] = 0.0;
-
- for (i = 0; i < 1 << 16; i++)
- {
- unsigned char c;
- unsigned short s;
+ unsigned char c;
+ unsigned short s;
- u.s[1] = i;
+ u.s[1] = i;
- if (u.f <= 0.0)
- {
- c = 0;
- s = 0;
- }
- else if (u.f >= 1.0)
- {
- c = 255;
- s = 65535;
- }
- else
- {
- c = rint (u.f * 255.0);
- s = rint (u.f * 65535.0);
- }
+ if (u.f <= 0.0)
+ {
+ c = 0;
+ s = 0;
+ }
+ else if (u.f >= 1.0)
+ {
+ c = 255;
+ s = 65535;
+ }
+ else
+ {
+ c = rint (u.f * 255.0);
+ s = rint (u.f * 65535.0);
+ }
/*fprintf (stderr, "%2.3f=%03i %05i ", f, c, (*hi));
/ if (! ((*hi)%9))
/ fprintf (stderr, "\n"); */
- table_F_8[u.s[1]] = c;
- table_F_16[u.s[1]] = s;
- }
- }
- /* fix tables to ensure 1:1 conversions back and forth */
- if (0)
- { /*FIXME: probably not the right way to do
it,.. must sit down and scribble on paper */
- int i;
- for (i = 0; i < 256; i++)
- {
- float f = table_8_F[i];
- unsigned short *hi = ((unsigned short *) (void *) &f);
- unsigned short *lo = ((unsigned short *) (void *) &f);
- *lo = 0;
- table_F_8[(*hi)] = i;
- }
+ table_F_8[u.s[1]] = c;
+ table_F_16[u.s[1]] = s;
}
+ /* fix tables to ensure 1:1 conversions back and forth */
+ for (i = 0; i < 256; i++)
+ {
+ u.f = table_8_F[i];
+ table_F_8[u.s[1]] = i;
+ }
}
/* function to find the index in table for a float */
-static unsigned int
+static INLINE unsigned int
gggl_float_to_index16 (float f)
{
union
@@ -904,6 +892,33 @@ conv_rgbaF_rgbA16 (unsigned char *src, u
return samples;
}
+#ifdef USE_TABLES
+
+static INLINE long
+conv_rgbaF_rgb8 (unsigned char *src, unsigned char *dst, long samples)
+{
+ long n = samples;
+ register float f;
+ float *fsrc = (float *) src;
+
+ while (n--)
+ {
+ f = (*(float *) fsrc++);
+ *(unsigned char *) dst++ = table_F_8[gggl_float_to_index16 (f)];
+
+ f = (*(float *) fsrc++);
+ *(unsigned char *) dst++ = table_F_8[gggl_float_to_index16 (f)];
+
+ f = (*(float *) fsrc++);
+ *(unsigned char *) dst++ = table_F_8[gggl_float_to_index16 (f)];
+
+ fsrc++;
+ }
+ return samples;
+}
+
+#else
+
static INLINE long
conv_rgbaF_rgb8 (unsigned char *src, unsigned char *dst, long samples)
{
@@ -924,6 +939,8 @@ conv_rgbaF_rgb8 (unsigned char *src, uns
return samples;
}
+#endif
+
static INLINE long
conv_rgbaF_g8 (unsigned char *src, unsigned char *dst, long samples)
{
@@ -1951,6 +1968,8 @@ init (void)
babl_component ("A"),
NULL);
+ table_init();
+
#define o(src, dst) \
babl_conversion_new (src, dst, "linear", conv_ ## src ## _ ## dst, NULL)
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