1 | /* |
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2 | * transupp.h |
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3 | * |
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4 | * Copyright (C) 1997-2001, Thomas G. Lane. |
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5 | * This file is part of the Independent JPEG Group's software. |
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6 | * For conditions of distribution and use, see the accompanying README file. |
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7 | * |
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8 | * This file contains declarations for image transformation routines and |
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9 | * other utility code used by the jpegtran sample application. These are |
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10 | * NOT part of the core JPEG library. But we keep these routines separate |
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11 | * from jpegtran.c to ease the task of maintaining jpegtran-like programs |
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12 | * that have other user interfaces. |
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13 | * |
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14 | * NOTE: all the routines declared here have very specific requirements |
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15 | * about when they are to be executed during the reading and writing of the |
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16 | * source and destination files. See the comments in transupp.c, or see |
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17 | * jpegtran.c for an example of correct usage. |
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18 | */ |
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19 | |
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20 | /* If you happen not to want the image transform support, disable it here */ |
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21 | #ifndef TRANSFORMS_SUPPORTED |
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22 | #define TRANSFORMS_SUPPORTED 1 /* 0 disables transform code */ |
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23 | #endif |
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24 | |
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25 | /* |
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26 | * Although rotating and flipping data expressed as DCT coefficients is not |
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27 | * hard, there is an asymmetry in the JPEG format specification for images |
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28 | * whose dimensions aren't multiples of the iMCU size. The right and bottom |
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29 | * image edges are padded out to the next iMCU boundary with junk data; but |
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30 | * no padding is possible at the top and left edges. If we were to flip |
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31 | * the whole image including the pad data, then pad garbage would become |
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32 | * visible at the top and/or left, and real pixels would disappear into the |
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33 | * pad margins --- perhaps permanently, since encoders & decoders may not |
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34 | * bother to preserve DCT blocks that appear to be completely outside the |
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35 | * nominal image area. So, we have to exclude any partial iMCUs from the |
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36 | * basic transformation. |
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37 | * |
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38 | * Transpose is the only transformation that can handle partial iMCUs at the |
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39 | * right and bottom edges completely cleanly. flip_h can flip partial iMCUs |
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40 | * at the bottom, but leaves any partial iMCUs at the right edge untouched. |
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41 | * Similarly flip_v leaves any partial iMCUs at the bottom edge untouched. |
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42 | * The other transforms are defined as combinations of these basic transforms |
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43 | * and process edge blocks in a way that preserves the equivalence. |
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44 | * |
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45 | * The "trim" option causes untransformable partial iMCUs to be dropped; |
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46 | * this is not strictly lossless, but it usually gives the best-looking |
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47 | * result for odd-size images. Note that when this option is active, |
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48 | * the expected mathematical equivalences between the transforms may not hold. |
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49 | * (For example, -rot 270 -trim trims only the bottom edge, but -rot 90 -trim |
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50 | * followed by -rot 180 -trim trims both edges.) |
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51 | * |
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52 | * We also offer a lossless-crop option, which discards data outside a given |
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53 | * image region but losslessly preserves what is inside. Like the rotate and |
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54 | * flip transforms, lossless crop is restricted by the JPEG format: the upper |
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55 | * left corner of the selected region must fall on an iMCU boundary. If this |
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56 | * does not hold for the given crop parameters, we silently move the upper left |
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57 | * corner up and/or left to make it so, simultaneously increasing the region |
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58 | * dimensions to keep the lower right crop corner unchanged. (Thus, the |
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59 | * output image covers at least the requested region, but may cover more.) |
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60 | * |
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61 | * If both crop and a rotate/flip transform are requested, the crop is applied |
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62 | * last --- that is, the crop region is specified in terms of the destination |
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63 | * image. |
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64 | * |
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65 | * We also offer a "force to grayscale" option, which simply discards the |
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66 | * chrominance channels of a YCbCr image. This is lossless in the sense that |
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67 | * the luminance channel is preserved exactly. It's not the same kind of |
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68 | * thing as the rotate/flip transformations, but it's convenient to handle it |
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69 | * as part of this package, mainly because the transformation routines have to |
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70 | * be aware of the option to know how many components to work on. |
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71 | */ |
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72 | |
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73 | |
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74 | /* Short forms of external names for systems with brain-damaged linkers. */ |
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75 | |
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76 | #ifdef NEED_SHORT_EXTERNAL_NAMES |
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77 | #define jtransform_parse_crop_spec jTrParCrop |
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78 | #define jtransform_request_workspace jTrRequest |
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79 | #define jtransform_adjust_parameters jTrAdjust |
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80 | #define jtransform_execute_transform jTrExec |
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81 | #define jtransform_perfect_transform jTrPerfect |
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82 | #define jcopy_markers_setup jCMrkSetup |
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83 | #define jcopy_markers_execute jCMrkExec |
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84 | #endif /* NEED_SHORT_EXTERNAL_NAMES */ |
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85 | |
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86 | |
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87 | /* |
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88 | * Codes for supported types of image transformations. |
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89 | */ |
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90 | |
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91 | typedef enum { |
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92 | JXFORM_NONE, /* no transformation */ |
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93 | JXFORM_FLIP_H, /* horizontal flip */ |
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94 | JXFORM_FLIP_V, /* vertical flip */ |
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95 | JXFORM_TRANSPOSE, /* transpose across UL-to-LR axis */ |
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96 | JXFORM_TRANSVERSE, /* transpose across UR-to-LL axis */ |
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97 | JXFORM_ROT_90, /* 90-degree clockwise rotation */ |
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98 | JXFORM_ROT_180, /* 180-degree rotation */ |
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99 | JXFORM_ROT_270 /* 270-degree clockwise (or 90 ccw) */ |
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100 | } JXFORM_CODE; |
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101 | |
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102 | /* |
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103 | * Codes for crop parameters, which can individually be unspecified, |
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104 | * positive, or negative. (Negative width or height makes no sense, though.) |
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105 | */ |
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106 | |
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107 | typedef enum { |
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108 | JCROP_UNSET, |
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109 | JCROP_POS, |
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110 | JCROP_NEG |
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111 | } JCROP_CODE; |
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112 | |
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113 | /* |
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114 | * Transform parameters struct. |
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115 | * NB: application must not change any elements of this struct after |
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116 | * calling jtransform_request_workspace. |
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117 | */ |
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118 | |
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119 | typedef struct { |
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120 | /* Options: set by caller */ |
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121 | JXFORM_CODE transform; /* image transform operator */ |
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122 | boolean perfect; /* if TRUE, fail if partial MCUs are requested */ |
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123 | boolean trim; /* if TRUE, trim partial MCUs as needed */ |
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124 | boolean force_grayscale; /* if TRUE, convert color image to grayscale */ |
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125 | boolean crop; /* if TRUE, crop source image */ |
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126 | |
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127 | /* Crop parameters: application need not set these unless crop is TRUE. |
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128 | * These can be filled in by jtransform_parse_crop_spec(). |
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129 | */ |
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130 | JDIMENSION crop_width; /* Width of selected region */ |
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131 | JCROP_CODE crop_width_set; |
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132 | JDIMENSION crop_height; /* Height of selected region */ |
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133 | JCROP_CODE crop_height_set; |
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134 | JDIMENSION crop_xoffset; /* X offset of selected region */ |
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135 | JCROP_CODE crop_xoffset_set; /* (negative measures from right edge) */ |
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136 | JDIMENSION crop_yoffset; /* Y offset of selected region */ |
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137 | JCROP_CODE crop_yoffset_set; /* (negative measures from bottom edge) */ |
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138 | |
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139 | /* Internal workspace: caller should not touch these */ |
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140 | int num_components; /* # of components in workspace */ |
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141 | jvirt_barray_ptr * workspace_coef_arrays; /* workspace for transformations */ |
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142 | JDIMENSION output_width; /* cropped destination dimensions */ |
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143 | JDIMENSION output_height; |
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144 | JDIMENSION x_crop_offset; /* destination crop offsets measured in iMCUs */ |
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145 | JDIMENSION y_crop_offset; |
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146 | int max_h_samp_factor; /* destination iMCU size */ |
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147 | int max_v_samp_factor; |
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148 | } jpeg_transform_info; |
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149 | |
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150 | |
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151 | #if TRANSFORMS_SUPPORTED |
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152 | |
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153 | /* Parse a crop specification (written in X11 geometry style) */ |
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154 | EXTERN(boolean) jtransform_parse_crop_spec |
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155 | JPP((jpeg_transform_info *info, const char *spec)); |
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156 | /* Request any required workspace */ |
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157 | EXTERN(void) jtransform_request_workspace |
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158 | JPP((j_decompress_ptr srcinfo, jpeg_transform_info *info)); |
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159 | /* Adjust output image parameters */ |
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160 | EXTERN(jvirt_barray_ptr *) jtransform_adjust_parameters |
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161 | JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, |
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162 | jvirt_barray_ptr *src_coef_arrays, |
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163 | jpeg_transform_info *info)); |
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164 | /* Execute the actual transformation, if any */ |
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165 | EXTERN(void) jtransform_execute_transform |
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166 | JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, |
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167 | jvirt_barray_ptr *src_coef_arrays, |
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168 | jpeg_transform_info *info)); |
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169 | /* Determine whether lossless transformation is perfectly |
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170 | * possible for a specified image and transformation. |
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171 | */ |
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172 | EXTERN(boolean) jtransform_perfect_transform |
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173 | JPP((JDIMENSION image_width, JDIMENSION image_height, |
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174 | int MCU_width, int MCU_height, |
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175 | JXFORM_CODE transform)); |
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176 | |
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177 | /* jtransform_execute_transform used to be called |
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178 | * jtransform_execute_transformation, but some compilers complain about |
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179 | * routine names that long. This macro is here to avoid breaking any |
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180 | * old source code that uses the original name... |
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181 | */ |
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182 | #define jtransform_execute_transformation jtransform_execute_transform |
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183 | |
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184 | #endif /* TRANSFORMS_SUPPORTED */ |
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185 | |
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186 | |
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187 | /* |
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188 | * Support for copying optional markers from source to destination file. |
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189 | */ |
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190 | |
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191 | typedef enum { |
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192 | JCOPYOPT_NONE, /* copy no optional markers */ |
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193 | JCOPYOPT_COMMENTS, /* copy only comment (COM) markers */ |
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194 | JCOPYOPT_ALL /* copy all optional markers */ |
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195 | } JCOPY_OPTION; |
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196 | |
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197 | #define JCOPYOPT_DEFAULT JCOPYOPT_COMMENTS /* recommended default */ |
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198 | |
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199 | /* Setup decompression object to save desired markers in memory */ |
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200 | EXTERN(void) jcopy_markers_setup |
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201 | JPP((j_decompress_ptr srcinfo, JCOPY_OPTION option)); |
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202 | /* Copy markers saved in the given source object to the destination object */ |
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203 | EXTERN(void) jcopy_markers_execute |
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204 | JPP((j_decompress_ptr srcinfo, j_compress_ptr dstinfo, |
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205 | JCOPY_OPTION option)); |
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