Rev 882 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 882 | serge | 1 | |
| 2 | #define CLIP_BOTTOM 2 |
||
| 3 | #define CLIP_RIGHT 4 |
||
| 4 | #define CLIP_LEFT 8 |
||
| 5 | |||
| 6 | |||
| 7 | |||
| 8 | /*================================= |
||
| 9 | |||
| 10 | |||
| 11 | { |
||
| 12 | int flag; |
||
| 1002 | serge | 13 | |
| 882 | serge | 14 | |
| 1002 | serge | 15 | if( x < clip->xmin ) { |
| 16 | flag |= CLIP_LEFT; |
||
| 882 | serge | 17 | } else if( x > clip->xmax ) { |
| 1002 | serge | 18 | flag |= CLIP_RIGHT; |
| 882 | serge | 19 | } |
| 1002 | serge | 20 | if( y < clip->ymin ) { |
| 21 | flag |= CLIP_TOP; |
||
| 882 | serge | 22 | } else if( y > clip->ymax ) { |
| 1002 | serge | 23 | flag |= CLIP_BOTTOM; |
| 882 | serge | 24 | } |
| 1002 | serge | 25 | return( flag ); |
| 26 | } |
||
| 882 | serge | 27 | |
| 28 | |||
| 29 | |||
| 30 | /*=========================================================================== |
||
| 31 | |||
| 32 | |||
| 33 | (x1, y1) is outside and ( x2, y2 ) is inside the viewport. |
||
| 34 | NOTE : the signs of denom and ( x - *x1 ) cancel out during division |
||
| 35 | so make both of them positive before rounding. */ |
||
| 36 | { |
||
| 37 | int numer; |
||
| 1002 | serge | 38 | int denom; |
| 39 | |||
| 882 | serge | 40 | |
| 1002 | serge | 41 | numer = 2L * (long)( y2 - *y1 ) * abs( x - *x1 ); |
| 42 | if( numer > 0 ) { |
||
| 43 | numer += denom; /* round to closest pixel */ |
||
| 882 | serge | 44 | } else { |
| 1002 | serge | 45 | numer -= denom; |
| 882 | serge | 46 | } |
| 1002 | serge | 47 | *y1 += numer / ( denom << 1 ); |
| 48 | *x1 = x; |
||
| 49 | } |
||
| 882 | serge | 50 | |
| 51 | |||
| 52 | |||
| 53 | /*============================================================= |
||
| 54 | |||
| 55 | |||
| 56 | viewport using the Cohen-Sutherland clipping algorithm. Return the |
||
| 57 | clipped coordinates and a decision drawing flag. */ |
||
| 58 | { |
||
| 59 | int flag1; |
||
| 1002 | serge | 60 | int flag2; |
| 61 | |||
| 882 | serge | 62 | |
| 1002 | serge | 63 | flag2 = _L1OutCode( clip, *x2, *y2 ); |
| 64 | for( ;; ) { |
||
| 65 | if( flag1 & flag2 ) break; /* trivially outside */ |
||
| 882 | serge | 66 | if( flag1 == flag2 ) break; /* completely inside */ |
| 67 | if( flag1 == 0 ) { /* first point inside */ |
||
| 68 | if( flag2 & CLIP_TOP ) { |
||
| 1002 | serge | 69 | line_inter( y2, x2, *y1, *x1, clip->ymin ); |
| 70 | } else if( flag2 & CLIP_BOTTOM ) { |
||
| 71 | line_inter( y2, x2, *y1, *x1, clip->ymax ); |
||
| 72 | } else if( flag2 & CLIP_RIGHT ) { |
||
| 73 | line_inter( x2, y2, *x1, *y1, clip->xmax ); |
||
| 74 | } else if( flag2 & CLIP_LEFT ) { |
||
| 75 | line_inter( x2, y2, *x1, *y1, clip->xmin ); |
||
| 76 | } |
||
| 77 | flag2 = _L1OutCode( clip, *x2, *y2 ); |
||
| 78 | } else { /* second point inside */ |
||
| 882 | serge | 79 | if( flag1 & CLIP_TOP ) { |
| 1002 | serge | 80 | line_inter( y1, x1, *y2, *x2, clip->ymin ); |
| 81 | } else if( flag1 & CLIP_BOTTOM ) { |
||
| 82 | line_inter( y1, x1, *y2, *x2, clip->ymax ); |
||
| 83 | } else if( flag1 & CLIP_RIGHT ) { |
||
| 84 | line_inter( x1, y1, *x2, *y2, clip->xmax ); |
||
| 85 | } else if( flag1 & CLIP_LEFT ) { |
||
| 86 | line_inter( x1, y1, *x2, *y2, clip->xmin ); |
||
| 87 | } |
||
| 88 | flag1 = _L1OutCode( clip, *x1, *y1 ); |
||
| 89 | } |
||
| 882 | serge | 90 | } |
| 1002 | serge | 91 | return( flag1 & flag2 ); |
| 92 | } |
||
| 882 | serge | 93 | |
| 94 | |||
| 95 | |||
| 96 | /*====================================================== |
||
| 97 | |||
| 98 | |||
| 99 | { |
||
| 100 | if( flag & CLIP_TOP ) { |
||
| 1002 | serge | 101 | *y = clip->ymin; |
| 882 | serge | 102 | } else if( flag & CLIP_BOTTOM ) { |
| 1002 | serge | 103 | *y = clip->ymax; |
| 882 | serge | 104 | } else if( flag & CLIP_RIGHT ) { |
| 1002 | serge | 105 | *x = clip->xmax; |
| 882 | serge | 106 | } else if( flag & CLIP_LEFT ) { |
| 1002 | serge | 107 | *x = clip->xmin; |
| 882 | serge | 108 | } |
| 1002 | serge | 109 | } |
| 882 | serge | 110 | |
| 111 | |||
| 112 | |||
| 113 | /*============================================================== |
||
| 114 | |||
| 115 | |||
| 116 | active viewport based on the Cohen-Sutherland algorithm for line |
||
| 117 | clipping. Return the clipped coordinates and a decision drawing |
||
| 118 | flag ( 0 draw : 1 don't draw ). */ |
||
| 119 | { |
||
| 120 | int flag1; |
||
| 1002 | serge | 121 | int flag2; |
| 122 | |||
| 882 | serge | 123 | |
| 1002 | serge | 124 | flag2 = _L1OutCode( clip, *x2, *y2 ); |
| 125 | for( ;; ) { |
||
| 126 | if( flag1 & flag2 ) break; /* trivially outside */ |
||
| 882 | serge | 127 | if( flag1 == flag2 ) break; /* completely inside */ |
| 128 | if( flag1 == 0 ) { |
||
| 129 | block_inter( clip, x2, y2, flag2 ); |
||
| 1002 | serge | 130 | flag2 = _L1OutCode( clip, *x2, *y2 ); |
| 131 | } else { |
||
| 882 | serge | 132 | block_inter( clip, x1, y1, flag1 ); |
| 1002 | serge | 133 | flag1 = _L1OutCode( clip, *x1, *y1 ); |
| 134 | } |
||
| 882 | serge | 135 | } |
| 1002 | serge | 136 | return( flag1 & flag2 ); |
| 137 | } |
||
| 882 | serge | 138 | |
| 139 | |||
| 140 | |||
| 141 | clip_t *src_clip,int *src_x, int *src_y, |
||
| 142 | int *w, int *h) |
||
| 143 | { |
||
| 144 | int sx0, sy0, sx1, sy1; |
||
| 1002 | serge | 145 | |
| 882 | serge | 146 | |
| 1002 | serge | 147 | sy0 = *src_y; |
| 148 | |||
| 882 | serge | 149 | |
| 1002 | serge | 150 | sy1 = sy0 + *h - 1; |
| 151 | |||
| 882 | serge | 152 | |
| 153 | |||
| 1002 | serge | 154 | { |
| 155 | int dx0, dy0, dx1, dy1; |
||
| 156 | |||
| 882 | serge | 157 | |
| 1002 | serge | 158 | dy0 = *dst_y + sy0 - *src_y; |
| 159 | |||
| 882 | serge | 160 | |
| 1002 | serge | 161 | dy1 = dy0 + sy1 - sy0; |
| 162 | |||
| 882 | serge | 163 | |
| 1002 | serge | 164 | { |
| 165 | *w = dx1 - dx0 + 1; |
||
| 166 | *h = dy1 - dy0 + 1; |
||
| 167 | |||
| 882 | serge | 168 | |
| 1002 | serge | 169 | *src_y += dy0 - *dst_y; |
| 170 | |||
| 882 | serge | 171 | |
| 1002 | serge | 172 | *dst_y = dy0; |
| 173 | |||
| 882 | serge | 174 | |
| 1002 | serge | 175 | }; |
| 176 | } |
||
| 177 | return 1; |
||
| 178 | }; |
||
| 882 | serge | 179 |