1 // Copyright 2024 Google LLC.
2 // Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
3 #include "tools/fiddle/examples.h"
4 REG_FIDDLE(SkSL_RawImageShaders, 384, 128, false, 0) {
make_image(sk_sp<SkRuntimeEffect> effect,const SkImageInfo & info)5 static sk_sp<SkImage> make_image(sk_sp<SkRuntimeEffect> effect,
6 const SkImageInfo& info) {
7 sk_sp<SkSurface> surface = SkSurfaces::Raster(info);
8 SkCanvas* canvas = surface->getCanvas();
9 auto shader = effect->makeShader(/*uniforms=*/ nullptr, /*children=*/ {});
10 if (!shader) {
11 return nullptr;
12 }
13 SkPaint paint;
14 paint.setShader(std::move(shader));
15 paint.setBlendMode(SkBlendMode::kSrc);
16 canvas->drawPaint(paint);
17 return surface->makeImageSnapshot();
18 }
19
draw(SkCanvas * canvas)20 void draw(SkCanvas* canvas) {
21 // Make a hemispherical normal map image:
22 auto imageInfo = SkImageInfo::MakeN32Premul(128, 128);
23 auto imageShader = SkRuntimeEffect::MakeForShader(SkString(R"(
24 vec4 main(vec2 p) {
25 p = (p / 128) * 2 - 1;
26 float len2 = dot(p, p);
27 vec3 v = (len2 > 1) ? vec3(0, 0, 1) : vec3(p, sqrt(1 - len2));
28 return (v * 0.5 + 0.5).xyz1;
29 })")).effect;
30 auto normalImage = make_image(imageShader, imageInfo);
31
32 // Make a simple lighting effect:
33 auto litEffect = SkRuntimeEffect::MakeForShader(SkString(R"(
34 uniform shader normals;
35 vec4 main(vec2 p) {
36 vec3 n = normalize(normals.eval(p).xyz * 2 - 1);
37 vec3 l = normalize(vec3(-1, -1, 0.5));
38 return saturate(dot(n, l)).xxx1;
39 })")).effect;
40 SkRuntimeShaderBuilder builder(litEffect);
41 SkPaint paint;
42
43 // FIRST: Draw the lighting to our (not color managed) canvas.
44 // This is our CORRECT, reference result:
45 builder.child("normals") = normalImage->makeShader(SkSamplingOptions{});
46 paint.setShader(builder.makeShader());
47 canvas->drawRect({0,0,128,128}, paint);
48
49 // Make an offscreen surface with a wide gamut:
50 auto rec2020 = SkColorSpace::MakeRGB(SkNamedTransferFn::kSRGB,
51 SkNamedGamut::kRec2020);
52 auto info = SkImageInfo::Make(128, 128, kRGBA_F16_SkColorType,
53 kPremul_SkAlphaType, rec2020);
54 auto surface = SkSurfaces::Raster(info);
55
56 // SECOND: Draw the lighting to the offscreen surface. Color management
57 // changes the normals, producing INCORRECT (wrong direction) lighting:
58 surface->getCanvas()->drawPaint(paint);
59 canvas->drawImage(surface->makeImageSnapshot(), 128, 0);
60
61 // THIRD: Convert the normals to a raw image shader. This ignores color
62 // management for that image, so we get CORRECT lighting again:
63 builder.child("normals") = normalImage->makeRawShader(SkSamplingOptions{});
64 paint.setShader(builder.makeShader());
65 surface->getCanvas()->drawPaint(paint);
66 canvas->drawImage(surface->makeImageSnapshot(), 256, 0);
67 }
68 } // END FIDDLE
69