1 files changed, 56 insertions, 1 deletions

diff --git a/mesalib/src/gallium/auxiliary/util/u_format_srgb.py b/mesalib/src/gallium/auxiliary/util/u_format_srgb.py
index cd63ae789..c6c02f053 100644
--- a/mesalib/src/gallium/auxiliary/util/u_format_srgb.py
+++ b/mesalib/src/gallium/auxiliary/util/u_format_srgb.py
@@ -40,6 +40,7 @@ CopyRight = '''
 
 
 import math
+import struct
 
 
 def srgb_to_linear(x):
@@ -51,10 +52,11 @@ def srgb_to_linear(x):
 
 def linear_to_srgb(x):
     if x >= 0.0031308:
-        return 1.055 * math.pow(x, 0.41666) - 0.055
+        return 1.055 * math.pow(x, 0.41666666) - 0.055
     else:
         return 12.92 * x
 
+
 def generate_srgb_tables():
     print 'const float'
     print 'util_format_srgb_8unorm_to_linear_float_table[256] = {'
@@ -84,6 +86,59 @@ def generate_srgb_tables():
     print '};'
     print
 
+# calculate the table interpolation values used in float linear to unorm8 srgb
+    numexp = 13
+    mantissa_msb = 3
+# stepshift is just used to only use every x-th float to make things faster,
+# 5 is largest value which still gives exact same table as 0
+    stepshift = 5
+    nbuckets = numexp << mantissa_msb
+    bucketsize = (1 << (23 - mantissa_msb)) >> stepshift
+    mantshift = 12
+    valtable = []
+    sum_aa = float(bucketsize)
+    sum_ab = 0.0
+    sum_bb = 0.0
+    for i in range(0, bucketsize):
+        j = (i << stepshift) >> mantshift
+        sum_ab += j
+        sum_bb += j*j
+    inv_det = 1.0 / (sum_aa * sum_bb - sum_ab * sum_ab)
+
+    for bucket in range(0, nbuckets):
+        start = ((127 - numexp) << 23) + bucket*(bucketsize << stepshift)
+        sum_a = 0.0
+        sum_b = 0.0
+ 
+        for i in range(0, bucketsize):
+            j = (i << stepshift) >> mantshift
+            fint = start + (i << stepshift)
+            ffloat = struct.unpack('f', struct.pack('I', fint))[0]
+            val = linear_to_srgb(ffloat) * 255.0 + 0.5
+            sum_a += val
+            sum_b += j*val
+
+        solved_a = inv_det * (sum_bb*sum_a - sum_ab*sum_b)
+        solved_b = inv_det * (sum_aa*sum_b - sum_ab*sum_a)
+
+        scaled_a = solved_a * 65536.0 / 512.0
+        scaled_b = solved_b * 65536.0
+ 
+        int_a = int(scaled_a + 0.5)
+        int_b = int(scaled_b + 0.5)
+
+        valtable.append((int_a << 16) + int_b)
+
+    print 'const unsigned'
+    print 'util_format_linear_to_srgb_helper_table[104] = {'
+
+    for j in range(0, nbuckets, 4):
+        print '   ',
+        for i in range(j, j + 4):
+            print '0x%08x,' % (valtable[i],),
+        print
+    print '};'
+    print
 
 def main():
     print '/* This file is autogenerated by u_format_srgb.py. Do not edit directly. */'