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@@ -83,36 +83,22 @@ swap( long int* a, long int* b ) |
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void
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dense_render_line( dense_worker* worker, TPos tox, TPos toy )
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{
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- // printf("line from: %d, %d to %d, %d\n", worker->prev_x, worker->prev_y,
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- // to_x, to_y);
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-
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FT26D6 fx = worker->prev_x>>2;
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FT26D6 fy = worker->prev_y>>2;
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-
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-
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- // float from_x = fx;
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- // float from_y = fy;
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FT26D6 from_x = fx;
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FT26D6 from_y = fy;
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-
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- // from_x /= 64.0;
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- // from_y /= 64.0;
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-
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FT26D6 tx = tox>>2;
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FT26D6 ty = toy>>2;
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- if ( fy == ty )
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- return;
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-
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- // float to_x = tx / 64.0;
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- // float to_y = ty / 64.0;
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FT26D6 to_x = tx;
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FT26D6 to_y = ty;
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-
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+ // from_x/y and to_x/y are coordinates in 26.6 format
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+ if ( from_y == to_y )
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+ return;
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//printf("line from: %f, %f to %f, %f\n", from_x, from_y, to_x, to_y);
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@@ -128,7 +114,7 @@ dense_render_line( dense_worker* worker, TPos tox, TPos toy ) |
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if ( from_y >= worker->m_h<<6 || to_y <= 0 )
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return;
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- //float dxdy = ( to_x - from_x ) / (float)( to_y - from_y );
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+
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FT26D6 deltax,deltay;
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deltax = to_x - from_x;
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deltay = to_y - from_y;
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@@ -139,26 +125,38 @@ dense_render_line( dense_worker* worker, TPos tox, TPos toy ) |
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from_y = 0;
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}
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- // TODO: test, imp line
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+ // This condition is important apparently
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if ( to_y > worker->m_h<<6 )
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{
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to_x -= (( to_y - worker->m_h<<6 ) * deltax/deltay);
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to_y = worker->m_h<<6;
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}
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- int x = from_x;
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+
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+ FT26D6 x = from_x;
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+
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+ // y-coordinate of first pixel of line
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int y0 = from_y>>6;
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+
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+ // y-coordinate of last pixel of line
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int y_limit = (to_y + 0x3f)>>6;
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- FT20D12* m_a = worker->m_a;
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+ FT20D12* m_a = worker->m_a;
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for ( int y = y0; y < y_limit; y++ )
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{
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- // printf("y is %d\n", y);
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int linestart = y * worker->m_w;
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+
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+ // dy is the height of the line present in the current scanline
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FT26D6 dy = min( (y + 1)<<6, to_y ) - max( y<<6, from_y );
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+
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+ // x coordinate where the line leaves the current scanline
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FT26D6 xnext = x + dy * deltax/deltay;
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+
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+ // height with sign
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FT26D6 d = dy * dir;
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+ // x0 is the x coordinate of the start of line in current scanline
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+ // x1 is the x coordinate of the end of line in current scanline
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FT26D6 x0, x1;
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if ( x < xnext )
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{
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| ... |
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@@ -171,48 +169,43 @@ dense_render_line( dense_worker* worker, TPos tox, TPos toy ) |
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x1 = x;
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}
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- /*
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- It's possible for x0 to be negative on the last scanline because of
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- floating-point inaccuracy That would cause an out-of-bounds array access at
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- index -1.
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- */
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- // float x0floor = x0 <= 0.0f ? 0.0f : (float)floor( x0 );
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-
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+ // x coordinate of the leftmost intersected pixel in the scanline
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int x0i = x0>>6;
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FT26D6 x0floor = x0i<<6;
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// float x1ceil = (float)ceil( x1 );
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+ // x coordinate of the rightmost intersected pixel in the scanline
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int x1i = (x1+0x3f)>>6;
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FT26D6 x1ceil = x1i <<6;
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if ( x1i <= x0i + 1 )
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{
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+ // average of x coordinates of trapezium with origin at left of pixel
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FT26D6 xmf = ( ( x + xnext )>>1) - x0floor;
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+
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+ // average of x coordinates of trapezium with origin at right of pixel
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m_a[linestart + x0i] += d * ((1<<6) - xmf);
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m_a[linestart + ( x0i + 1 )] += d * xmf;
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}
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else
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{
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- // float s = 1.0f / ( x1 - x0 );
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198
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- // float x0f = x0 - x0floor;
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- // float a0 = 0.5f * s * ( 1.0f - x0f ) * ( 1.0f - x0f );
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- // float x1f = x1 - x1ceil + 1.0f;
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- // float am = 0.5f * s * x1f * x1f;
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+ // total horizontal length of line in current scanline, might be replaced by deltax
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FT26D6 oneOverS = x1 - x0;
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FT26D6 x0f = x0 - x0floor;
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197
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-
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+ // 64 - x0f is the horizontal length of line in first pixel
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FT26D6 oneMinusX0f = (1<<6) - x0f;
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+
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+ // Stores area of triangle in first pixel divided by d
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FT26D6 a0 = ((oneMinusX0f * oneMinusX0f) >> 1) / oneOverS;
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+
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+ // x1f is the horizontal length in the last pixel
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FT26D6 x1f = x1 - x1ceil + (1<<6);
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FT26D6 am = ((x1f * x1f) >> 1) / oneOverS;
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- // printf("x0 is %lld, x1 is %lld\n",x0,x1 );
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-
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-
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-
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+ // d * a0 is area of triangle in first pixel
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m_a[linestart + x0i] += d * a0;
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if ( x1i == x0i + 2 )
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| ... |
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@@ -224,12 +217,15 @@ dense_render_line( dense_worker* worker, TPos tox, TPos toy ) |
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217
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FT26D6 dTimesS = (d << 12) / oneOverS;
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- for ( FT26D6 xi = x0i + 2; xi < x1i - 1; xi++ )
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+ for ( FT26D6 xi = x0i + 2; xi < x1i - 1; xi++ ){
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+ // Increase area for successive pixels by dy/dx
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m_a[linestart + xi] += dTimesS;
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+ }
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FT26D6 a2 = a1 + (( x1i - x0i - 3 )<<12)/oneOverS;
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m_a[linestart + ( x1i - 1 )] += d * ( (1<<6) - a2 - am );
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}
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+ // Area in last pixel of scanline
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m_a[linestart + x1i] += d * am;
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}
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x = xnext;
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| ... |
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@@ -459,22 +455,6 @@ dense_render_glyph( dense_worker* worker, const FT_Bitmap* target ) |
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dest++;
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}
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- // float value = 0.0f;
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- // while ( dest < dest_end )
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- // {
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- // value += *source++;
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- // if ( value > 0.0f )
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- // {
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- // int n = (int)( fabs( value ) * 255.0f + 0.5f );
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- // if ( n > 255 )
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- // n = 255;
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- // *dest = (unsigned char)n;
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- // }
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- // else
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- // *dest = 0;
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- // dest++;
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- // }
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477
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-
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free(worker->m_a);
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return error;
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460
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}
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