1 #! /usr/bin/python

     2 # Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).

     3 #

     4 # Permission is hereby granted, free of charge, to any person obtaining a

     5 # copy of this software and /or associated documentation files

     6 # (the "Materials "), to deal in the Materials without restriction,

     7 # including without limitation the rights to use, copy, modify, merge,

     8 # publish, distribute, sublicense, and/or sell copies of the Materials,

     9 # and to permit persons to whom the Materials are furnished to do so,

    10 # subject to the following conditions:

    11 #

    12 # The above copyright notice and this permission notice shall be included

    13 # in all copies or substantial portions of the Materials.

    14 #

    15 # THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

    16 # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

    17 # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

    18 # IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,

    19 # DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR

    20 # OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE MATERIALS OR

    21 # THE USE OR OTHER DEALINGS IN THE MATERIALS.

    22 

    23 from c_utils import *

    24 

    25 # \todo Might require a more accurate table for lookups.

    26 

    27 RCP_BITS = 8

    28 RCP_DATATYPE_BITS = RCP_BITS + 8

    29 

    30 def tofx(f):

    31     return int(f * (1<<RCP_BITS) + 0.5)

    32 

    33 def alpha_to_uintrcp(alpha):

    34     if alpha == 0:

    35         rf = 255 # Max out

    36     else:

    37         rf = 255.0/alpha

    38     i = tofx(rf)

    39     assert(i < (1<<RCP_DATATYPE_BITS))

    40     return i

    41 

    42 def test_error():

    43     max_err = 0

    44     for alpha in range(1, 256):

    45         for color in range(0, 256):

    46             if color > alpha:

    47                 # Undefined result -> ignore test.

    48                 continue

    49             fa = alpha / 255.0

    50             fc = color / 255.0

    51             ex = fc / fa

    52             exi = int(ex * 255.0 + 0.5)

    53             ia = alpha_to_uintrcp(alpha)

    54             m = (ia * color) >> RCP_BITS

    55             e = abs(exi - m)

    56             if e > max_err:

    57                 print ia * color

    58                 print alpha, color, exi, m, fa, fc, ex, ia / float(1<<RCP_BITS), ia

    59                 max_err = e

    60     print max_err

    61     return max_err

    62 

    63 if __name__ == '__main__':

    64     vals = []

    65     for alpha in range(0, 256):

    66        i = alpha_to_uintrcp(alpha)

    67        vals += [i]

    68     

    69     begin_include_guard("_SFALPHARCP_H_") 

    70     print ""

    71     make_include("riDefs.h")

    72     print ""

    73     begin_namespace("OpenVGRI")

    74     make_constant("ALPHA_RCP_BITS", RCP_BITS)

    75     make_array("static const", "RIuint16", "sc_alphaRcp", vals, hex_formatter)

    76     end_namespace()

    77     end_include_guard()

    78