1 | <?php |
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2 | |
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3 | /** |
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4 | * @file |
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5 | * Functions for the generation of the CAPTCHA image. |
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6 | * |
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7 | * Loosely Based on MyCaptcha by Heine Deelstra |
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8 | * (http://heine.familiedeelstra.com/mycaptcha-download) |
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9 | */ |
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10 | |
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11 | /** |
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12 | * Menu callback function that generates the CAPTCHA image. |
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13 | */ |
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14 | function image_captcha_image($captcha_sid=NULL) { |
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15 | // If output buffering is on: discard current content and disable further buffering |
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16 | if (ob_get_level()) { |
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17 | ob_end_clean(); |
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18 | } |
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19 | |
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20 | if (!$captcha_sid) { |
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21 | exit(); |
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22 | } |
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23 | |
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24 | // Get solution (the code to show). |
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25 | $code = db_result(db_query("SELECT solution FROM {captcha_sessions} WHERE csid = %d", (int)($captcha_sid))); |
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26 | |
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27 | // Only generate captcha if code exists in the session. |
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28 | if ($code !== FALSE) { |
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29 | // generate the image |
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30 | $image = @_image_captcha_generate_image($code); |
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31 | // check of generation was successful |
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32 | if (!$image) { |
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33 | watchdog('CAPTCHA', 'Generation of image CAPTCHA failed. Check your image CAPTCHA configuration and especially the used font.', array(), WATCHDOG_ERROR); |
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34 | exit(); |
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35 | } |
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36 | // Send the image resource as an image file to the client. |
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37 | $file_format = variable_get('image_captcha_file_format', IMAGE_CAPTCHA_FILE_FORMAT_JPG); |
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38 | if ($file_format == IMAGE_CAPTCHA_FILE_FORMAT_JPG) { |
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39 | drupal_set_header("Content-type: image/jpeg"); |
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40 | imagejpeg($image); |
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41 | } |
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42 | else { |
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43 | drupal_set_header("Content-type: image/png"); |
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44 | imagepng($image); |
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45 | } |
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46 | // Clean up the image resource. |
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47 | imagedestroy($image); |
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48 | } |
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49 | exit(); |
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50 | } |
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51 | |
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52 | |
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53 | /** |
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54 | * Small helper function for parsing a hexadecimal color to a RGB tuple. |
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55 | */ |
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56 | function _image_captcha_hex_to_rgb($hex) { |
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57 | // handle #RGB format |
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58 | if (strlen($hex) == 4) { |
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59 | $hex = $hex[1] . $hex[1] . $hex[2] . $hex[2] . $hex[3] . $hex[3]; |
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60 | } |
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61 | $c = hexdec($hex); |
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62 | $rgb = array(); |
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63 | for ($i = 16; $i >= 0; $i -= 8) { |
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64 | $rgb[] = ($c >> $i) & 0xFF; |
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65 | } |
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66 | return $rgb; |
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67 | } |
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68 | |
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69 | /** |
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70 | * Base function for generating a image CAPTCHA. |
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71 | */ |
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72 | function _image_captcha_generate_image($code) { |
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73 | // Get font. |
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74 | $fonts = _image_captcha_get_enabled_fonts(); |
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75 | |
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76 | // get other settings |
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77 | $font_size = (int) variable_get('image_captcha_font_size', 30); |
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78 | $character_spacing = (float) variable_get('image_captcha_character_spacing', '1.2'); |
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79 | $characters = _image_captcha_utf8_split($code); |
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80 | $character_quantity = count($characters); |
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81 | $width = $character_spacing * $font_size * $character_quantity; |
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82 | $height = 2 * $font_size; |
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83 | |
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84 | // create image resource |
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85 | $image = imagecreatetruecolor($width, $height); |
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86 | if (!$image) { |
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87 | return FALSE; |
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88 | } |
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89 | |
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90 | // Get the background color and paint the background. |
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91 | $background_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_background_color', '#ffffff')); |
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92 | $background_color = imagecolorallocate($image, $background_rgb[0], $background_rgb[1], $background_rgb[2]); |
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93 | // Set transparency if needed. |
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94 | $file_format = variable_get('image_captcha_file_format', IMAGE_CAPTCHA_FILE_FORMAT_JPG); |
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95 | if ($file_format == IMAGE_CAPTCHA_FILE_FORMAT_TRANSPARENT_PNG) { |
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96 | imagecolortransparent($image, $background_color); |
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97 | } |
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98 | imagefilledrectangle($image, 0, 0, $width, $height, $background_color); |
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99 | |
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100 | // Do we need to draw in RTL mode? |
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101 | global $language; |
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102 | $rtl = $language->direction && ((bool) variable_get('image_captcha_rtl_support', 0)); |
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103 | |
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104 | // draw text |
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105 | $result = _image_captcha_image_generator_print_string($image, $width, $height, $fonts, $font_size, $code, $rtl); |
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106 | if (!$result) { |
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107 | return FALSE; |
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108 | } |
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109 | |
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110 | // add noise |
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111 | $noise_colors = array(); |
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112 | for ($i = 0; $i < 20; $i++) { |
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113 | $noise_colors[] = imagecolorallocate($image, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255)); |
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114 | } |
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115 | // Add additional noise. |
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116 | if (variable_get('image_captcha_dot_noise', 0)) { |
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117 | _image_captcha_image_generator_add_dots($image, $width, $height, $noise_colors); |
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118 | } |
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119 | if (variable_get('image_captcha_line_noise', 0)) { |
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120 | _image_captcha_image_generator_add_lines($image, $width, $height, $noise_colors); |
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121 | } |
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122 | |
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123 | // Distort the image. |
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124 | $distortion_amplitude = .25 * $font_size * variable_get('image_captcha_distortion_amplitude', 0) / 10.0; |
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125 | if ($distortion_amplitude > 1) { |
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126 | // distortion parameters |
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127 | $wavelength_xr = (2+3*lcg_value())*$font_size; |
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128 | $wavelength_yr = (2+3*lcg_value())*$font_size; |
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129 | $freq_xr = 2 * 3.141592 / $wavelength_xr; |
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130 | $freq_yr = 2 * 3.141592 / $wavelength_yr; |
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131 | $wavelength_xt = (2+3*lcg_value())*$font_size; |
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132 | $wavelength_yt = (2+3*lcg_value())*$font_size; |
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133 | $freq_xt = 2 * 3.141592 / $wavelength_xt; |
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134 | $freq_yt = 2 * 3.141592 / $wavelength_yt; |
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135 | |
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136 | $distorted_image = imagecreatetruecolor($width, $height); |
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137 | if ($file_format == IMAGE_CAPTCHA_FILE_FORMAT_TRANSPARENT_PNG) { |
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138 | imagecolortransparent($distorted_image, $background_color); |
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139 | } |
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140 | if (!$distorted_image) { |
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141 | return FALSE; |
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142 | } |
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143 | |
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144 | if (variable_get('image_captcha_bilinear_interpolation', FALSE)) { |
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145 | // distortion with bilinear interpolation |
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146 | for ($x = 0; $x < $width; $x++) { |
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147 | for ($y = 0; $y < $height; $y++) { |
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148 | // get distorted sample point in source image |
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149 | $r = $distortion_amplitude * sin($x * $freq_xr + $y * $freq_yr); |
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150 | $theta = $x * $freq_xt + $y * $freq_yt; |
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151 | $sx = $x + $r * cos($theta); |
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152 | $sy = $y + $r * sin($theta); |
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153 | $sxf = (int)floor($sx); |
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154 | $syf = (int)floor($sy); |
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155 | if ($sxf < 0 || $syf < 0 || $sxf >= $width - 1 || $syf >= $height - 1) { |
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156 | $color = $background_color; |
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157 | } |
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158 | else { |
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159 | // bilinear interpolation: sample at four corners |
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160 | $color_00 = imagecolorat($image, $sxf , $syf ); |
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161 | $color_00_r = ($color_00 >> 16) & 0xFF; |
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162 | $color_00_g = ($color_00 >> 8) & 0xFF; |
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163 | $color_00_b = $color_00 & 0xFF; |
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164 | $color_10 = imagecolorat($image, $sxf+1, $syf ); |
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165 | $color_10_r = ($color_10 >> 16) & 0xFF; |
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166 | $color_10_g = ($color_10 >> 8) & 0xFF; |
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167 | $color_10_b = $color_10 & 0xFF; |
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168 | $color_01 = imagecolorat($image, $sxf , $syf+1); |
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169 | $color_01_r = ($color_01 >> 16) & 0xFF; |
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170 | $color_01_g = ($color_01 >> 8) & 0xFF; |
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171 | $color_01_b = $color_01 & 0xFF; |
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172 | $color_11 = imagecolorat($image, $sxf+1, $syf+1); |
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173 | $color_11_r = ($color_11 >> 16) & 0xFF; |
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174 | $color_11_g = ($color_11 >> 8) & 0xFF; |
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175 | $color_11_b = $color_11 & 0xFF; |
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176 | // interpolation factors |
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177 | $u = $sx - $sxf; |
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178 | $v = $sy - $syf; |
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179 | // interpolate |
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180 | $r = (int)((1-$v)*((1-$u)*$color_00_r + $u*$color_10_r) + $v*((1-$u)*$color_01_r + $u*$color_11_r)); |
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181 | $g = (int)((1-$v)*((1-$u)*$color_00_g + $u*$color_10_g) + $v*((1-$u)*$color_01_g + $u*$color_11_g)); |
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182 | $b = (int)((1-$v)*((1-$u)*$color_00_b + $u*$color_10_b) + $v*((1-$u)*$color_01_b + $u*$color_11_b)); |
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183 | // build color |
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184 | $color = ($r<<16) + ($g<<8) + $b; |
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185 | } |
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186 | imagesetpixel($distorted_image, $x, $y, $color); |
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187 | } |
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188 | } |
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189 | } |
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190 | else { |
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191 | // distortion with nearest neighbor interpolation |
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192 | for ($x = 0; $x < $width; $x++) { |
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193 | for ($y = 0; $y < $height; $y++) { |
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194 | // get distorted sample point in source image |
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195 | $r = $distortion_amplitude * sin($x * $freq_xr + $y * $freq_yr); |
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196 | $theta = $x * $freq_xt + $y * $freq_yt; |
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197 | $sx = $x + $r * cos($theta); |
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198 | $sy = $y + $r * sin($theta); |
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199 | $sxf = (int)floor($sx); |
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200 | $syf = (int)floor($sy); |
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201 | if ($sxf < 0 || $syf < 0 || $sxf >= $width - 1 || $syf >= $height - 1) { |
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202 | $color = $background_color; |
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203 | } |
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204 | else { |
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205 | $color = imagecolorat($image, $sxf, $syf); |
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206 | } |
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207 | imagesetpixel($distorted_image, $x, $y, $color); |
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208 | } |
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209 | } |
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210 | } |
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211 | // release undistorted image |
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212 | imagedestroy($image); |
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213 | // return distorted image |
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214 | return $distorted_image; |
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215 | } |
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216 | else { |
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217 | return $image; |
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218 | } |
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219 | } |
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220 | |
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221 | function _image_captcha_image_generator_add_lines(&$image, $width, $height, $colors) { |
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222 | $line_quantity = $width * $height/200.0 * ((int) variable_get('image_captcha_noise_level', 5)) / 10.0; |
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223 | for ($i = 0; $i < $line_quantity; $i++) { |
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224 | imageline($image, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $colors[array_rand($colors)]); |
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225 | } |
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226 | } |
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227 | |
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228 | function _image_captcha_image_generator_add_dots(&$image, $width, $height, $colors) { |
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229 | $noise_quantity = $width * $height * ((int) variable_get('image_captcha_noise_level', 5)) / 10.0; |
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230 | for ($i = 0; $i < $noise_quantity; $i++ ) { |
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231 | imagesetpixel($image, mt_rand(0, $width), mt_rand(0, $height), $colors[array_rand($colors)]); |
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232 | } |
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233 | } |
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234 | |
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235 | /** |
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236 | * Helper function for drawing text on the image. |
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237 | */ |
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238 | function _image_captcha_image_generator_print_string(&$image, $width, $height, $fonts, $font_size, $text, $rtl=FALSE) { |
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239 | // get characters |
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240 | $characters = _image_captcha_utf8_split($text); |
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241 | $character_quantity = count($characters); |
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242 | |
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243 | // get colors |
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244 | $background_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_background_color', '#ffffff')); |
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245 | $foreground_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_foreground_color', '#000000')); |
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246 | $background_color = imagecolorallocate($image, $background_rgb[0], $background_rgb[1], $background_rgb[2]); |
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247 | $foreground_color = imagecolorallocate($image, $foreground_rgb[0], $foreground_rgb[1], $foreground_rgb[2]); |
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248 | // precalculate the value ranges for color randomness |
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249 | $foreground_randomness = (int)(variable_get('image_captcha_foreground_color_randomness', 100)); |
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250 | if ($foreground_randomness) { |
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251 | $foreground_color_range = array(); |
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252 | for ($i=0; $i<3; $i++) { |
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253 | $foreground_color_range[$i] = array(max(0, $foreground_rgb[$i] - $foreground_randomness), min(255, $foreground_rgb[$i] + $foreground_randomness)); |
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254 | } |
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255 | } |
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256 | |
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257 | // set default text color |
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258 | $color = $foreground_color; |
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259 | |
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260 | // the image is seperated in different character cages, one for each character |
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261 | // each character will be somewhere inside that cage |
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262 | $ccage_width = $width / $character_quantity; |
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263 | $ccage_height = $height; |
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264 | |
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265 | foreach ($characters as $c => $character) { |
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266 | // initial position of character: in the center of its cage |
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267 | $center_x = ($c + 0.5) * $ccage_width; |
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268 | if ($rtl) { |
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269 | $center_x = $width - $center_x; |
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270 | } |
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271 | $center_y = 0.5 * $height; |
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272 | |
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273 | // Pick a random font from the list. |
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274 | $font = $fonts[array_rand($fonts)]; |
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275 | |
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276 | // Get character dimensions for TrueType fonts. |
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277 | if ($font != 'BUILTIN') { |
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278 | $bbox = imagettfbbox($font_size, 0, realpath($font), $character); |
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279 | // In very rare cases with some versions of the GD library, the x-value |
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280 | // of the left side of the bounding box as returned by the first call of |
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281 | // imagettfbbox is corrupt (value -2147483648 = 0x80000000). |
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282 | // The weird thing is that calling the function a second time |
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283 | // can be used as workaround. |
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284 | // This issue is discussed at http://drupal.org/node/349218. |
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285 | if ($bbox[2] < 0) { |
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286 | $bbox = imagettfbbox($font_size, 0, realpath($font), $character); |
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287 | } |
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288 | } |
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289 | else { |
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290 | $character_width = imagefontwidth(5); |
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291 | $character_height = imagefontheight(5); |
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292 | $bbox = array(0, $character_height, $character_width, $character_height, $character_width, 0, 0, 0); |
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293 | } |
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294 | |
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295 | // Random (but small) rotation of the character. |
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296 | // TODO: add a setting for this? |
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297 | $angle = mt_rand(-10, 10); |
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298 | |
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299 | // Determine print position: at what coordinate should the character be |
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300 | // printed so that the bounding box would be nicely centered in the cage? |
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301 | $bb_center_x = .5 * ($bbox[0] + $bbox[2]); |
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302 | $bb_center_y = .5 * ($bbox[1] + $bbox[7]); |
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303 | $angle_cos = cos($angle*3.1415/180); |
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304 | $angle_sin = sin($angle*3.1415/180); |
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305 | $pos_x = $center_x - ($angle_cos * $bb_center_x + $angle_sin * $bb_center_y); |
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306 | $pos_y = $center_y - (-$angle_sin * $bb_center_x + $angle_cos * $bb_center_y); |
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307 | |
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308 | // Calculate available room to jitter: how much can the character be moved |
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309 | // so that it stays inside its cage? |
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310 | $bb_width = $bbox[2] - $bbox[0]; |
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311 | $bb_height = $bbox[1] - $bbox[7]; |
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312 | $dev_x = .5 * max(0, $ccage_width - abs($angle_cos) * $bb_width - abs($angle_sin) * $bb_height); |
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313 | $dev_y = .5 * max(0, $ccage_height - abs($angle_cos) * $bb_height - abs($angle_sin) * $bb_width); |
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314 | |
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315 | // add jitter to position |
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316 | $pos_x = $pos_x + mt_rand(-$dev_x, $dev_x); |
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317 | $pos_y = $pos_y + mt_rand(-$dev_y, $dev_y); |
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318 | |
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319 | // calculate text color in case of randomness |
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320 | if ($foreground_randomness) { |
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321 | $color = imagecolorallocate($image, |
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322 | mt_rand($foreground_color_range[0][0], $foreground_color_range[0][1]), |
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323 | mt_rand($foreground_color_range[1][0], $foreground_color_range[1][1]), |
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324 | mt_rand($foreground_color_range[2][0], $foreground_color_range[2][1]) |
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325 | ); |
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326 | } |
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327 | |
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328 | // draw character |
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329 | if ($font == 'BUILTIN') { |
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330 | imagestring($image, 5, $pos_x, $pos_y, $character, $color); |
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331 | } |
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332 | else { |
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333 | imagettftext($image, $font_size, $angle, $pos_x, $pos_y, $color, realpath($font), $character); |
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334 | } |
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335 | |
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336 | // For debugging purposes: draw character bounding box (only valid when rotation is disabled). |
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337 | // imagerectangle($image, $pos_x + $bbox[0], $pos_y + $bbox[1], $pos_x + $bbox[2], $pos_y + $bbox[7], $color); |
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338 | |
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339 | } |
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340 | |
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341 | // return a sign of success |
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342 | return TRUE; |
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343 | } |
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