1 | /* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */ |
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2 | #include "dxReaderCommon.h" |
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3 | #include "GradientFilter.h" |
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4 | |
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5 | #include "Vector3.h" |
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6 | #include "stdlib.h" |
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7 | |
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8 | float * |
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9 | merge(float *scalar, float *gradient, int size) |
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10 | { |
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11 | float *data = (float *)malloc(sizeof(float) * 4 * size); |
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12 | |
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13 | Vector3 *g = (Vector3 *)gradient; |
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14 | |
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15 | int ngen = 0, sindex = 0; |
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16 | for (sindex = 0; sindex < size; ++sindex) { |
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17 | data[ngen++] = scalar[sindex]; |
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18 | data[ngen++] = 1.0 - g[sindex].x; |
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19 | data[ngen++] = 1.0 - g[sindex].y; |
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20 | data[ngen++] = 1.0 - g[sindex].z; |
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21 | } |
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22 | return data; |
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23 | } |
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24 | |
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25 | void |
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26 | normalizeScalar(float *fdata, int count, float min, float max) |
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27 | { |
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28 | float v = max - min; |
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29 | if (v != 0.0f) { |
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30 | for (int i = 0; i < count; ++i) { |
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31 | if (fdata[i] != -1.0) { |
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32 | fdata[i] = (fdata[i] - min)/ v; |
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33 | } |
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34 | } |
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35 | } |
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36 | } |
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37 | |
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38 | /** |
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39 | * \brief Compute Sobel filtered gradients for a 3D volume |
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40 | * |
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41 | * This technique is fairly expensive in terms of memory and |
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42 | * running time due to the filter extent. |
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43 | */ |
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44 | float * |
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45 | computeGradient(float *fdata, |
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46 | int width, int height, int depth, |
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47 | float dx, float dy, float dz, |
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48 | float min, float max) |
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49 | { |
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50 | float *gradients = (float *)malloc(width * height * depth * 3 * |
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51 | sizeof(float)); |
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52 | float *tempGradients = (float *)malloc(width * height * depth * 3 * |
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53 | sizeof(float)); |
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54 | int sizes[3] = { width, height, depth }; |
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55 | float spacing[3] = { dx, dy, dz }; |
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56 | computeGradients(tempGradients, fdata, sizes, spacing, DATRAW_FLOAT); |
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57 | filterGradients(tempGradients, sizes); |
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58 | quantizeGradients(tempGradients, gradients, sizes, DATRAW_FLOAT); |
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59 | free(tempGradients); |
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60 | normalizeScalar(fdata, width * height * depth, min, max); |
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61 | float *data = merge(fdata, gradients, width * height * depth); |
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62 | free(gradients); |
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63 | return data; |
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64 | } |
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65 | |
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66 | /** |
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67 | * \brief Compute gradients for a 3D volume with cubic cells |
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68 | * |
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69 | * The gradients are estimated using the central difference |
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70 | * method. This function assumes the data are normalized |
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71 | * to [0,1] with missing data/NaNs represented by a negative |
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72 | * value. |
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73 | * |
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74 | * \param data Data array with X the fastest running. There |
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75 | * should be 4 floats allocated for each node, with the |
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76 | * first float containing the scalar value. The subsequent |
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77 | * 3 floats will be filled with the x,y,z components of the |
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78 | * gradient vector |
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79 | * \param nx The number of nodes in the X direction |
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80 | * \param ny The number of nodes in the Y direction |
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81 | * \param nz The number of nodes in the Z direction |
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82 | * \param dx The spacing (cell length) in the X direction |
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83 | * \param dy The spacing (cell length) in the Y direction |
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84 | * \param dz The spacing (cell length) in the Z direction |
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85 | */ |
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86 | void |
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87 | computeSimpleGradient(float *data, int nx, int ny, int nz, |
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88 | float dx, float dy, float dz) |
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89 | { |
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90 | bool clampToEdge = true; |
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91 | double borderVal = 0.0; |
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92 | |
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93 | #define BORDER ((clampToEdge ? data[ngen] : borderVal)) |
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94 | |
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95 | // Compute the gradient of this data. BE CAREFUL: center |
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96 | // calculation on each node to avoid skew in either direction. |
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97 | int ngen = 0; |
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98 | for (int iz = 0; iz < nz; iz++) { |
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99 | for (int iy = 0; iy < ny; iy++) { |
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100 | for (int ix = 0; ix < nx; ix++) { |
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101 | // gradient in x-direction |
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102 | double valm1 = (ix == 0) ? BORDER : data[ngen - 4]; |
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103 | double valp1 = (ix == nx-1) ? BORDER : data[ngen + 4]; |
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104 | if (valm1 < 0.0 || valp1 < 0.0) { |
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105 | data[ngen+1] = 0.0; |
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106 | } else { |
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107 | data[ngen+1] = -(valp1-valm1)/(2. * dx); |
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108 | } |
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109 | |
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110 | // gradient in y-direction |
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111 | valm1 = (iy == 0) ? BORDER : data[ngen - 4*nx]; |
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112 | valp1 = (iy == ny-1) ? BORDER : data[ngen + 4*nx]; |
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113 | if (valm1 < 0.0 || valp1 < 0.0) { |
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114 | data[ngen+2] = 0.0; |
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115 | } else { |
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116 | data[ngen+2] = -(valp1-valm1)/(2. * dy); |
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117 | } |
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118 | |
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119 | // gradient in z-direction |
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120 | valm1 = (iz == 0) ? BORDER : data[ngen - 4*nx*ny]; |
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121 | valp1 = (iz == nz-1) ? BORDER : data[ngen + 4*nx*ny]; |
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122 | if (valm1 < 0.0 || valp1 < 0.0) { |
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123 | data[ngen+3] = 0.0; |
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124 | } else { |
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125 | data[ngen+3] = -(valp1-valm1)/(2. * dz); |
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126 | } |
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127 | // Normalize and scale/bias to [0,1] range |
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128 | // The volume shader will expand to [-1,1] |
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129 | double len = sqrt(data[ngen+1]*data[ngen+1] + |
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130 | data[ngen+2]*data[ngen+2] + |
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131 | data[ngen+3]*data[ngen+3]); |
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132 | if (len < 1.0e-6) { |
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133 | data[ngen+1] = 0.0; |
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134 | data[ngen+2] = 0.0; |
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135 | data[ngen+3] = 0.0; |
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136 | } else { |
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137 | data[ngen+1] = (data[ngen+1]/len + 1.0) * 0.5; |
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138 | data[ngen+2] = (data[ngen+2]/len + 1.0) * 0.5; |
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139 | data[ngen+3] = (data[ngen+3]/len + 1.0) * 0.5; |
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140 | } |
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141 | ngen += 4; |
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142 | } |
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143 | } |
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144 | } |
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145 | |
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146 | #undef BORDER |
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147 | } |
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