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Revert "bring back lowp bilerp_clamp_8888"

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This reverts commit 5043c09b8b.

Reason for revert: speculative, to try to unblock android roller

Original change's description:
> bring back lowp bilerp_clamp_8888
> 
> PS1-3 are the literal code I removed a few months ago.
> 
> PS4 adds asserts to make sure we don't underflow.
> PS5 adds rounding when scaling off bias, reducing diff slightly.
> 
> Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
> Change-Id: Ice573395a1680e1c3b55a8fe3e4d034f15adde1b
> Reviewed-on: https://skia-review.googlesource.com/c/196620
> Commit-Queue: Mike Klein <mtklein@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=mtklein@google.com,brianosman@google.com,reed@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I816c23c4a12451be518ea3baf4b9a3fdba9b818a
Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Reviewed-on: https://skia-review.googlesource.com/c/196777
Reviewed-by: Mike Reed <reed@google.com>
This commit is contained in:
Mike Reed 2019-03-03 13:06:14 +00:00
parent 1b9f889628
commit c6671be0ea
1 changed files with 1 additions and 67 deletions
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68
src/opts/SkRasterPipeline_opts.h
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@ -3273,73 +3273,6 @@ STAGE_PP(srcover_rgba_8888, const SkRasterPipeline_MemoryCtx* ctx) {
store_8888_(ptr, tail, r,g,b,a);
}
#if defined(SK_DISABLE_LOWP_BILERP_CLAMP_CLAMP_STAGE)
static void(*bilerp_clamp_8888)(void) = nullptr;
#else
STAGE_GP(bilerp_clamp_8888, const SkRasterPipeline_GatherCtx* ctx) {
// (cx,cy) are the center of our sample.
F cx = x,
cy = y;
// All sample points are at the same fractional offset (fx,fy).
// They're the 4 corners of a logical 1x1 pixel surrounding (x,y) at (0.5,0.5) offsets.
F fx = fract(cx + 0.5f),
fy = fract(cy + 0.5f);
// We'll accumulate the color of all four samples into {r,g,b,a} directly.
r = g = b = a = 0;
// The first three sample points will calculate their area using math
// just like in the float code above, but the fourth will take up all the rest.
//
// Logically this is the same as doing the math for the fourth pixel too,
// but rounding error makes this a better strategy, keeping opaque opaque, etc.
//
// We can keep up to 8 bits of fractional precision without overflowing 16-bit,
// so our "1.0" area is 256.
const uint16_t bias = 256;
U16 remaining = bias;
for (float dy = -0.5f; dy <= +0.5f; dy += 1.0f)
for (float dx = -0.5f; dx <= +0.5f; dx += 1.0f) {
// (x,y) are the coordinates of this sample point.
F x = cx + dx,
y = cy + dy;
// ix_and_ptr() will clamp to the image's bounds for us.
const uint32_t* ptr;
U32 ix = ix_and_ptr(&ptr, ctx, x,y);
U16 sr,sg,sb,sa;
from_8888(gather<U32>(ptr, ix), &sr,&sg,&sb,&sa);
// In bilinear interpolation, the 4 pixels at +/- 0.5 offsets from the sample pixel center
// are combined in direct proportion to their area overlapping that logical query pixel.
// At positive offsets, the x-axis contribution to that rectangle is fx,
// or (1-fx) at negative x. Same deal for y.
F sx = (dx > 0) ? fx : 1.0f - fx,
sy = (dy > 0) ? fy : 1.0f - fy;
U16 area = (dy == 0.5f && dx == 0.5f) ? remaining
: cast<U16>(sx * sy * bias);
for (size_t i = 0; i < N; i++) {
SkASSERT(remaining[i] >= area[i]);
}
remaining -= area;
r += sr * area;
g += sg * area;
b += sb * area;
a += sa * area;
}
r = (r + bias/2) / bias;
g = (g + bias/2) / bias;
b = (b + bias/2) / bias;
a = (a + bias/2) / bias;
}
#endif
// Now we'll add null stand-ins for stages we haven't implemented in lowp.
// If a pipeline uses these stages, it'll boot it out of lowp into highp.
#define NOT_IMPLEMENTED(st) static void (*st)(void) = nullptr;
@ -3387,6 +3320,7 @@ STAGE_GP(bilerp_clamp_8888, const SkRasterPipeline_GatherCtx* ctx) {
NOT_IMPLEMENTED(mirror_y)
NOT_IMPLEMENTED(repeat_y)
NOT_IMPLEMENTED(negate_x)
NOT_IMPLEMENTED(bilerp_clamp_8888)
NOT_IMPLEMENTED(bilinear_nx)
NOT_IMPLEMENTED(bilinear_ny)
NOT_IMPLEMENTED(bilinear_px)