gallium: Move sRGB <-> RGB handling to libmesautil

Signed-off-by: Jason Ekstrand <[email protected]>
Reviewed-by: Marek Olšák <[email protected]>

1 files changed, 155 insertions, 0 deletions

diff --git a/src/util/format_srgb.py b/src/util/format_srgb.py
new file mode 100644
index 00000000000..d5cbcf7646b
--- /dev/null
+++ b/src/util/format_srgb.py
@@ -0,0 +1,155 @@
+#!/usr/bin/env python
+
+CopyRight = '''
+/**************************************************************************
+ *
+ * Copyright 2010 VMware, Inc.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+
+/**
+ * @file
+ * SRGB translation.
+ *
+ * @author Brian Paul <[email protected]>
+ * @author Michal Krol <[email protected]>
+ * @author Jose Fonseca <[email protected]>
+ */
+'''
+
+
+import math
+import struct
+
+
+def srgb_to_linear(x):
+    if x <= 0.04045:
+        return x / 12.92
+    else:
+        return math.pow((x + 0.055) / 1.055, 2.4)
+
+
+def linear_to_srgb(x):
+    if x >= 0.0031308:
+        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] = {'
+    for j in range(0, 256, 4):
+        print '   ',
+        for i in range(j, j + 4):
+            print '%.7e,' % (srgb_to_linear(i / 255.0),),
+        print
+    print '};'
+    print
+    print 'const uint8_t'
+    print 'util_format_srgb_to_linear_8unorm_table[256] = {'
+    for j in range(0, 256, 16):
+        print '   ',
+        for i in range(j, j + 16):
+            print '%3u,' % (int(srgb_to_linear(i / 255.0) * 255.0 + 0.5),),
+        print
+    print '};'
+    print
+    print 'const uint8_t'
+    print 'util_format_linear_to_srgb_8unorm_table[256] = {'
+    for j in range(0, 256, 16):
+        print '   ',
+        for i in range(j, j + 16):
+            print '%3u,' % (int(linear_to_srgb(i / 255.0) * 255.0 + 0.5),),
+        print
+    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. */'
+    print
+    # This will print the copyright message on the top of this file
+    print CopyRight.strip()
+    print
+    print '#include "format_srgb.h"'
+    print
+    generate_srgb_tables()
+
+
+if __name__ == '__main__':
+    main()