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1 // Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies). |
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2 // All rights reserved. |
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3 // This component and the accompanying materials are made available |
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4 // under the terms of "Eclipse Public License v1.0" |
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5 // which accompanies this distribution, and is available |
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6 // at the URL "http://www.eclipse.org/legal/epl-v10.html". |
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7 // |
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8 // Initial Contributors: |
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9 // Nokia Corporation - initial contribution. |
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10 // |
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11 // Contributors: |
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12 // |
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13 // Description: |
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14 // |
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15 |
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16 #ifndef __BLENDINGALGORITHMS_H__ |
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17 #define __BLENDINGALGORITHMS_H__ |
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18 |
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19 #include <e32def.h> |
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20 /** |
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21 @file |
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22 @internalTechnology |
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23 */ |
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24 |
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25 /** Premultiplied Alpha (PMA) Blending algorithm. |
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26 Assumes src and target pixels are in PMA format (i.e., the color channels are already multiplied |
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27 with the alpha channel. |
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28 Blending Equations: |
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29 Cd' = Cs + ((255 - As) * Cd)/255 |
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30 Ad' = As + ((255 - As) * Ad)/255 |
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31 where Cd' and Ad' are destination values for color and alpha channels respectively, after blending, |
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32 Cd and Ad are destination values before blending, and Cs and As are source values (color and |
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33 alpha values respectively). |
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34 Optimisations: |
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35 Use of 256 instead of 255 converts the division to shift (faster). |
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36 Red and Blue channels are calculated together in one 32 bit operation. |
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37 Alpha and Green channels are calculated in the same way. However, due the |
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38 position of these channels within the pixel format, an extra shift is required. |
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39 The equations used are: |
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40 Cd' = Cs + (((0x100 - As) * Cd)>>8) |
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41 Ad' = As + (((0x100 - As) * Ad)>>8) |
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42 For the results to not overflow, it is required that the value of any of the color channels |
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43 is no greater than the alpha channel, which is what is exepected of pma format. |
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44 It is also assumed that the aMask is equal to source alpha. |
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45 @param aDestPixel The destination pixel value. |
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46 @param aSrcPixel The source pixel value. |
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47 @param aMask The source alpha. It is assumed to be same as source alpha. |
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48 @return the alpha-blended pixel (within the PMA space). |
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49 @internalTechnology |
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50 @released |
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51 */ |
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52 inline TUint32 PMAPixelBlend(TUint32 aDestPixel, TUint32 aSrcPixel, TUint8 aMask); |
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53 |
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54 /** Same as inline TUint32 PMAPixelBlend(TUint32 aDestPixel, TUint32 aSrcPixel, TUint8 aMask) |
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55 Calls inline TUint32 PMAPixelBlend(TUint32 aDestPixel, TUint32 aSrcPixel, TUint8 aMask), with aMask |
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56 extracted from the source pixel. |
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57 @see PMAPixelBlend(TUint32 aDestPixel, TUint32 aSrcPixel, TUint8 aMask) |
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58 @internalTechnology |
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59 @released |
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60 */ |
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61 inline TUint32 PMAPixelBlend(TUint32 aDestPixel, TUint32 aSrcPixel); |
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62 |
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63 /** |
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64 Does the premultiplied alpha blend, but does not check for any pre/post conditions. |
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65 Please DO NOT Add any optimisations to check for these conditions in this code! |
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66 @internalTechnology |
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67 @released |
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68 */ |
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69 inline TUint32 PMABlend_noChecks(TUint32 aDestPixel, TUint32 aSrcPixel, TUint8 aMaskingFactor); |
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70 |
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71 /** |
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72 The version of PMABlend_noChecks which does the blending in place. |
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73 @internalTechnology |
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74 @released |
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75 */ |
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76 inline void PMABlend_noChecksInplace(TUint32& aDest_io, const TUint32& aSrcPixel, TUint8 aMaskingFactor); |
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77 |
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78 /** |
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79 The in-place version of the PMAPixelBlend algorithm |
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80 @internalTechnology |
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81 @released |
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82 */ |
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83 inline void PMAInplaceBlend(TUint32& aDest_io, TUint32& aSrc_in); |
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84 /** |
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85 Premultiplies the color channel values with the Alpha channel value. |
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86 Alpha value remains unchanged. An approximation is used in the operation where the division |
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87 by 255 is approximated by a shift-by-8-bits operation (i.e. division by 256). |
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88 @param aPixel The 32 bit pixel value to be pre-multiplied. |
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89 @return The PMA value. |
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90 @internalTechnology |
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91 @released |
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92 */ |
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93 inline TUint32 NonPMA2PMAPixel(TUint32 aPixel); |
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94 |
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95 /** |
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96 Divives the PMA pixel color channels with the Alpha value, to convert them to non-PMA format. |
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97 Alpha value remains unchanged. |
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98 @param aPixel the premultiplied 32 bit pixel value. |
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99 @param aNormTable The lookup table used to do the normalisation (the table converts the division |
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100 to multiplication operation). |
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101 The table is usually obtainable by a call to the method: |
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102 PtrTo16BitNormalisationTable, which is defined in lookuptable.dll(.lib). |
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103 The lookup table for normalised alpha is compluted using this equation: |
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104 Table[index] = (255*256) / index (where index is an 8 bit value). |
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105 @return The NON-PMA 32 bit pixel value. |
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106 @internalTechnology |
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107 @released |
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108 */ |
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109 inline TUint32 PMA2NonPMAPixel(TUint32 aPixel, const TUint16* aNormTable); |
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110 |
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111 /** |
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112 In-place version of NonPMA2PMAPixel. |
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113 @see NonPMA2PMAPixel |
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114 @internalTechnology |
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115 @released |
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116 */ |
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117 inline void Convert2PMA(TUint32& aInOutValue); |
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118 |
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119 /** |
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120 In-place version of PMA2NonPMAPixel |
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121 @see PMA2NonPMAPixel |
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122 @internalTechnology |
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123 @released |
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124 */ |
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125 inline void Convert2NonPMA(TUint32& aInOutValue, const TUint16* aNormTable); |
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126 |
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127 #include <graphics/blendingalgorithms.inl> |
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128 |
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129 #endif //__BLENDINGALGORITHMS_H__ |