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Fix and uncomment non-MMX version.
Thu Jan 3 19:31:58 2002 Owen Taylor <otaylor@redhat.com> * pixops/pixops.c (scale_line_22_33): Fix and uncomment non-MMX version. * pixops/pixops.c (pixops_composite_nearest): Remove a division. * pixops/pixops.c (pixops_composite): Add some docs about the parameters. * pixops/README: Add notes about the correct algorithms for alpha compositing and how to implement them quickly.
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Owen Taylor
Owen Taylor
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@ -1,3 +1,17 @@
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Thu Jan 3 19:31:58 2002 Owen Taylor <otaylor@redhat.com>
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* pixops/pixops.c (scale_line_22_33): Fix and uncomment
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non-MMX version.
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* pixops/pixops.c (pixops_composite_nearest): Remove a
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division.
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* pixops/pixops.c (pixops_composite): Add some docs
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about the parameters.
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* pixops/README: Add notes about the correct algorithms
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for alpha compositing and how to implement them quickly.
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2001-12-29 Tor Lillqvist <tml@iki.fi>
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* Makefile.am (EXTRA_DIST): Add makefile.msc.
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@ -33,6 +33,61 @@ for a number of the most common special cases:
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compositing from RGBA to RGBx
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compositing against a color from RGBA and storing in a RGBx buffer
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Alpha compositing 8 bit RGBAa onto RGB is defined in terms of
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rounding the exact result (real values in [0,1]):
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cc = ca * aa + (1 - aa) * Cb
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Cc = ROUND [255. * (Ca/255. * Aa/255. + (1 - Aa/255.) * Cb/255.)]
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We can comp
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ROUND(i / 255.) can be computed exactly for i in [0,255*255] as:
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t = i + 0x80; result = (t + (t >> 8)) >> 8; [ call this as To8(i) ]
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So,
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t = Ca * Aa + (255 - Aa) * Cb + 0x80;
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Cc = (t + (t >> 8)) >> 8;
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Alpha compositing 8 bit RaGaBaAa onto RbGbBbAa is a little harder, for
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non-premultiplied alpha. The premultiplied result is simple:
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ac = aa + (1 - aa) * ab
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cc = ca + (1 - aa) * cb
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Which can be computed in integers terms as:
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Cc = Ca + To8 ((255 - Aa) * Cb)
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Ac = Aa + To8 ((255 - Aa) * Ab)
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For non-premultiplied alpha, we need divide the color components by
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the alpha:
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+- (ca * aa + (1 - aa) * ab * cb)) / ac; aa != 0
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cc = |
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+- cb; aa == 0
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To calculate this as in integer, we note the alternate form:
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cc = cb + aa * (ca - cb) / ac
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[ 'cc = ca + (ac - aa) * (cb - ca) / ac' can also be useful numerically,
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but isn't important here ]
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We can express this as integers as:
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Ac_tmp = Aa * 255 + (255 - Aa) * Ab;
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+- Cb + (255 * Aa * (Ca - Cb) + Ac_tmp / 2) / Ac_tmp ; Ca > Cb
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Cc = |
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+- Cb - (255 * Aa * (Cb - Ca) + Ac_tmp / 2) / Ac_tmp ; ca <= Cb
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Or, playing bit tricks to avoid the conditional
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Cc = Cb + (255 * Aa * (Ca - Cb) + (((Ca - Cb) >> 8) ^ (Ac_tmp / 2)) ) / Ac_tmp
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TODO
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====
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@ -57,13 +112,13 @@ TODO
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the _nearest() variants do it right, most of the other code
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is wrong to some degree or another.
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For instance, in composite line, we have:
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For instance, in composite_line_22_4a4(), we have:
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dest[0] = ((0xff0000 - a) * dest[0] + r) >> 24;
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if a is 0, then we have:
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if a is 0 (implies r == 0), then we have:
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(0xff0000 * dest[0] + r) >> 24
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(0xff0000 * dest[0]) >> 24
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which gives results which are 1 to low:
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@ -202,10 +202,14 @@ pixops_composite_nearest (guchar *dest_buf,
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else
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{
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unsigned int a1 = 0xff - a0;
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dest[0] = (a0 * p[0] + a1 * dest[0]) / 0xff;
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dest[1] = (a0 * p[1] + a1 * dest[1]) / 0xff;
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dest[2] = (a0 * p[2] + a1 * dest[2]) / 0xff;
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unsigned int tmp;
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tmp = a0 * p[0] + a1 * dest[0] + 0x80;
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dest[0] = (tmp + (tmp >> 8)) >> 8;
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tmp = a0 * p[1] + a1 * dest[1] + 0x80;
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dest[1] = (tmp + (tmp >> 8)) >> 8;
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tmp = a0 * p[2] + a1 * dest[2] + 0x80;
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dest[2] = (tmp + (tmp >> 8)) >> 8;
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}
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break;
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}
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@ -388,7 +392,7 @@ composite_line (int *weights, int n_x, int n_y,
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int *pixel_weights;
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pixel_weights = weights + ((x >> (SCALE_SHIFT - SUBSAMPLE_BITS)) & SUBSAMPLE_MASK) * n_x * n_y;
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for (i=0; i<n_y; i++)
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{
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guchar *q = src[i] + x_scaled * src_channels;
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@ -837,10 +841,9 @@ scale_line_22_33_mmx_stub (int *weights, int n_x, int n_y,
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}
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#endif /* USE_MMX */
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#ifdef SCALE_LINE_22_33_USED /* This dead code would need changes if we wanted to use it */
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static guchar *
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scale_line_22_33 (int *weights, int n_x, int n_y,
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guchar *dest, guchar *dest_end, int dest_channels, int dest_has_alpha,
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guchar *dest, int dest_x, guchar *dest_end, int dest_channels, int dest_has_alpha,
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guchar **src, int src_channels, gboolean src_has_alpha,
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int x_init, int x_step, int src_width,
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int check_size, guint32 color1, guint32 color2)
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@ -860,8 +863,8 @@ scale_line_22_33 (int *weights, int n_x, int n_y,
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q0 = src0 + x_scaled * 3;
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q1 = src1 + x_scaled * 3;
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pixel_weights = (int *)((char *)weights + ((x >> (SCALE_SHIFT - SUBSAMPLE_BITS - 4)) & (SUBSAMPLE_MASK << 4)));
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pixel_weights = weights + ((x >> (SCALE_SHIFT - SUBSAMPLE_BITS)) & SUBSAMPLE_MASK) * 4;
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w1 = pixel_weights[0];
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w2 = pixel_weights[1];
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w3 = pixel_weights[2];
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@ -883,9 +886,9 @@ scale_line_22_33 (int *weights, int n_x, int n_y,
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g += w4 * q1[5];
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b += w4 * q1[6];
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dest[0] = r >> 16;
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dest[1] = g >> 16;
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dest[2] = b >> 16;
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dest[0] = (r + 0x8000) >> 16;
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dest[1] = (g + 0x8000) >> 16;
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dest[2] = (b + 0x8000) >> 16;
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dest += 3;
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@ -894,7 +897,6 @@ scale_line_22_33 (int *weights, int n_x, int n_y,
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return dest;
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}
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#endif /* SCALE_LINE_22_33_USED */
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static void
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process_pixel (int *weights, int n_x, int n_y,
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@ -1227,7 +1229,7 @@ bilinear_make_fast_weights (PixopsFilter *filter, double x_scale, double y_scale
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for (i = 0; i < n_y; i++)
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for (j = 0; j < n_x; j++)
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*(pixel_weights + n_x * i + j) = 65536 * x_weights[j] * x_scale * y_weights[i] * y_scale * overall_alpha;
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*(pixel_weights + n_x * i + j) = 65536 * x_weights[j] * x_scale * y_weights[i] * y_scale * overall_alpha + 0.5;
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}
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g_free (x_weights);
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@ -1412,6 +1414,30 @@ pixops_composite_color (guchar *dest_buf,
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g_free (filter.weights);
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}
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/**
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* pixops_composite:
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* @dest_buf: pointer to location to store result
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* @render_x0: x0 of region of scaled source to store into @dest_buf
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* @render_y0: y0 of region of scaled source to store into @dest_buf
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* @render_x1: x1 of region of scaled source to store into @dest_buf
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* @render_y1: x1 of region of scaled source to store into @dest_buf
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* @dest_rowstride: rowstride of @dest_buf
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* @dest_channels: number of channels in @dest_buf
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* @dest_has_alpha: whether @dest_buf has alpha
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* @src_buf: pointer to source pixels
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* @src_width: width of source (used for clipping)
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* @src_height: height of source (used for clipping)
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* @src_rowstride: rowstride of source
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* @src_channels: number of channels in @src_buf
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* @src_has_alpha: whether @src_buf has alpha
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* @scale_x: amount to scale source by in X direction
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* @scale_y: amount to scale source by in Y direction
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* @interp_type: type of enumeration
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* @overall_alpha: overall alpha factor to multiply source by
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*
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* Scale source buffer by scale_x / scale_y, then composite a given rectangle
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* of the result into the destination buffer.
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**/
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void
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pixops_composite (guchar *dest_buf,
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int render_x0,
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@ -1550,12 +1576,16 @@ pixops_scale (guchar *dest_buf,
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break;
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}
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if (filter.n_x == 2 && filter.n_y == 2 && dest_channels == 3 && src_channels == 3)
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{
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#ifdef USE_MMX
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if (filter.n_x == 2 && filter.n_y == 2 &&
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found_mmx && dest_channels == 3 && src_channels == 3)
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line_func = scale_line_22_33_mmx_stub;
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if (found_mmx)
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line_func = scale_line_22_33_mmx_stub;
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else
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#endif
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line_func = scale_line_22_33;
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}
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else
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#endif
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line_func = scale_line;
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pixops_process (dest_buf, render_x0, render_y0, render_x1, render_y1,
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@ -55,6 +55,12 @@ _pixops_scale_line_22_33_mmx:
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cmpl %esi,28(%ebp)
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je .out
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/* For the body of this loop, %mm01, %mm1, %mm2, %mm3 hold the 4 adjoining
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* points we are interpolating between, as:
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*
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* 000000BB00GG00RR
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*/
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/* Load initial values into %mm1, %mm3 */
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leal (%edx,%edx,2),%edx # Multiply by 3
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@ -82,11 +88,16 @@ _pixops_scale_line_22_33_mmx:
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jmp .newx
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.p2align 4,,7
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.loop:
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/* int x_index = (x & 0xf000) >> 12 */
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/* short *pixel_weights = weights + ((x >> (SCALE_SHIFT - SUBSAMPLE_BITS)) & SUBSAMPLE_MASK) * n_x * n_y
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* 16 4 0xf 2 2
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*/
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movl %ebx,%eax
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andl $0xf000,%eax
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shrl $7,%eax
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/* At this point, %edi holds weights. Load the 4 weights into %mm4,%mm5,%mm6,%mm7, multiply and
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* accumulate.
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*/
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movq (%edi,%eax),%mm4
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pmullw %mm0,%mm4
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movq 8(%edi,%eax),%mm5
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@ -99,7 +110,17 @@ _pixops_scale_line_22_33_mmx:
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paddw %mm6, %mm7
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paddw %mm5, %mm7
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/* %mm7 holds the accumulated sum. Compute (C + 0x80) / 256
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*/
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pxor %mm4, %mm4
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movl $8421504, %eax # 0x00808080
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movd %eax, %mm6
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punpcklbw %mm4, %mm6
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paddw %mm6, %mm7
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psrlw $8, %mm7
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/* Pack into %eax and store result
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*/
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packuswb %mm7, %mm7
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movd %mm7, %eax
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@ -113,7 +134,7 @@ _pixops_scale_line_22_33_mmx:
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/* x += x_step; */
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addl 24(%ebp),%ebx
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/* x_scale = x >> 16; */
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/* x_scaled = x >> 16; */
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movl %ebx,%edx
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sarl $16,%edx
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@ -131,7 +152,6 @@ _pixops_scale_line_22_33_mmx:
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leal (%edx,%edx,2),%edx # Multiply by 3
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movl 16(%ebp),%edi
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pxor %mm4, %mm4
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movzbl 2(%edi,%edx),%ecx
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shll $16,%ecx
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movzwl (%edi,%edx),%eax
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