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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1029 | serge | 1 | |
| 2 | #define CLIP_BOTTOM 2 |
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| 3 | #define CLIP_RIGHT 4 |
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| 4 | #define CLIP_LEFT 8 |
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| 5 | |||
| 6 | |||
| 7 | |||
| 8 | /*================================= |
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| 9 | |||
| 10 | |||
| 11 | { |
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| 12 | int flag; |
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| 13 | |||
| 14 | |||
| 15 | if( x < clip->xmin ) { |
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| 16 | flag |= CLIP_LEFT; |
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| 17 | } else if( x > clip->xmax ) { |
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| 18 | flag |= CLIP_RIGHT; |
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| 19 | } |
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| 20 | if( y < clip->ymin ) { |
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| 21 | flag |= CLIP_TOP; |
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| 22 | } else if( y > clip->ymax ) { |
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| 23 | flag |= CLIP_BOTTOM; |
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| 24 | } |
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| 25 | return( flag ); |
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| 26 | } |
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| 27 | |||
| 28 | |||
| 29 | |||
| 30 | /*=========================================================================== |
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| 31 | |||
| 32 | |||
| 33 | (x1, y1) is outside and ( x2, y2 ) is inside the viewport. |
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| 34 | NOTE : the signs of denom and ( x - *x1 ) cancel out during division |
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| 35 | so make both of them positive before rounding. */ |
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| 36 | { |
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| 37 | int numer; |
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| 38 | int denom; |
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| 39 | |||
| 40 | |||
| 41 | numer = 2L * (long)( y2 - *y1 ) * abs( x - *x1 ); |
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| 42 | if( numer > 0 ) { |
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| 43 | numer += denom; /* round to closest pixel */ |
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| 44 | } else { |
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| 45 | numer -= denom; |
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| 46 | } |
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| 47 | *y1 += numer / ( denom << 1 ); |
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| 48 | *x1 = x; |
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| 49 | } |
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| 50 | |||
| 51 | |||
| 52 | |||
| 53 | /*============================================================= |
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| 54 | |||
| 55 | |||
| 56 | viewport using the Cohen-Sutherland clipping algorithm. Return the |
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| 57 | clipped coordinates and a decision drawing flag. */ |
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| 58 | { |
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| 59 | int flag1; |
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| 60 | int flag2; |
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| 61 | |||
| 62 | |||
| 63 | flag2 = _L1OutCode( clip, *x2, *y2 ); |
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| 64 | for( ;; ) { |
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| 65 | if( flag1 & flag2 ) break; /* trivially outside */ |
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| 66 | if( flag1 == flag2 ) break; /* completely inside */ |
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| 67 | if( flag1 == 0 ) { /* first point inside */ |
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| 68 | if( flag2 & CLIP_TOP ) { |
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| 69 | line_inter( y2, x2, *y1, *x1, clip->ymin ); |
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| 70 | } else if( flag2 & CLIP_BOTTOM ) { |
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| 71 | line_inter( y2, x2, *y1, *x1, clip->ymax ); |
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| 72 | } else if( flag2 & CLIP_RIGHT ) { |
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| 73 | line_inter( x2, y2, *x1, *y1, clip->xmax ); |
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| 74 | } else if( flag2 & CLIP_LEFT ) { |
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| 75 | line_inter( x2, y2, *x1, *y1, clip->xmin ); |
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| 76 | } |
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| 77 | flag2 = _L1OutCode( clip, *x2, *y2 ); |
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| 78 | } else { /* second point inside */ |
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| 79 | if( flag1 & CLIP_TOP ) { |
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| 80 | line_inter( y1, x1, *y2, *x2, clip->ymin ); |
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| 81 | } else if( flag1 & CLIP_BOTTOM ) { |
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| 82 | line_inter( y1, x1, *y2, *x2, clip->ymax ); |
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| 83 | } else if( flag1 & CLIP_RIGHT ) { |
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| 84 | line_inter( x1, y1, *x2, *y2, clip->xmax ); |
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| 85 | } else if( flag1 & CLIP_LEFT ) { |
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| 86 | line_inter( x1, y1, *x2, *y2, clip->xmin ); |
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| 87 | } |
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| 88 | flag1 = _L1OutCode( clip, *x1, *y1 ); |
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| 89 | } |
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| 90 | } |
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| 91 | return( flag1 & flag2 ); |
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| 92 | } |
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| 93 | |||
| 94 | |||
| 95 | |||
| 96 | /*====================================================== |
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| 97 | |||
| 98 | |||
| 99 | { |
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| 100 | if( flag & CLIP_TOP ) { |
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| 101 | *y = clip->ymin; |
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| 102 | } else if( flag & CLIP_BOTTOM ) { |
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| 103 | *y = clip->ymax; |
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| 104 | } else if( flag & CLIP_RIGHT ) { |
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| 105 | *x = clip->xmax; |
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| 106 | } else if( flag & CLIP_LEFT ) { |
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| 107 | *x = clip->xmin; |
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| 108 | } |
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| 109 | } |
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| 110 | |||
| 111 | |||
| 112 | |||
| 113 | /*============================================================== |
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| 114 | |||
| 115 | |||
| 116 | active viewport based on the Cohen-Sutherland algorithm for line |
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| 117 | clipping. Return the clipped coordinates and a decision drawing |
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| 118 | flag ( 0 draw : 1 don't draw ). */ |
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| 119 | { |
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| 120 | int flag1; |
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| 121 | int flag2; |
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| 122 | |||
| 123 | |||
| 124 | flag2 = _L1OutCode( clip, *x2, *y2 ); |
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| 125 | for( ;; ) { |
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| 126 | if( flag1 & flag2 ) break; /* trivially outside */ |
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| 127 | if( flag1 == flag2 ) break; /* completely inside */ |
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| 128 | if( flag1 == 0 ) { |
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| 129 | block_inter( clip, x2, y2, flag2 ); |
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| 130 | flag2 = _L1OutCode( clip, *x2, *y2 ); |
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| 131 | } else { |
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| 132 | block_inter( clip, x1, y1, flag1 ); |
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| 133 | flag1 = _L1OutCode( clip, *x1, *y1 ); |
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| 134 | } |
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| 135 | } |
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| 136 | return( flag1 & flag2 ); |
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| 137 | } |
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| 138 | |||
| 139 | |||
| 140 | |||
| 141 | clip_t *src_clip,int *src_x, int *src_y, |
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| 142 | int *w, int *h) |
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| 143 | { |
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| 144 | int sx0, sy0, sx1, sy1; |
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| 145 | |||
| 146 | |||
| 147 | sy0 = *src_y; |
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| 148 | |||
| 149 | |||
| 150 | sy1 = sy0 + *h - 1; |
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| 151 | |||
| 152 | |||
| 153 | |||
| 154 | { |
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| 155 | int dx0, dy0, dx1, dy1; |
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| 156 | |||
| 157 | |||
| 158 | dy0 = *dst_y + sy0 - *src_y; |
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| 159 | |||
| 160 | |||
| 161 | dy1 = dy0 + sy1 - sy0; |
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| 162 | |||
| 163 | |||
| 164 | { |
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| 165 | *w = dx1 - dx0 + 1; |
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| 166 | *h = dy1 - dy0 + 1; |
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| 167 | |||
| 168 | |||
| 169 | *src_y += dy0 - *dst_y; |
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| 170 | |||
| 171 | |||
| 172 | *dst_y = dy0; |
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| 173 | |||
| 174 | |||
| 175 | }; |
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| 176 | return 1; |
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| 177 | } |
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| 178 | return 1; |
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| 179 | }; |
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| 180 |