gm/runtimecolorfilter.cpp

/*
 * Copyright 2019 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "gm/gm.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkColorFilter.h"
#include "include/core/SkData.h"
#include "include/core/SkImage.h"
#include "include/core/SkPaint.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkSize.h"
#include "include/core/SkString.h"
#include "include/effects/SkRuntimeEffect.h"
#include "tools/Resources.h"

#include <stddef.h>
#include <utility>

const char* gLumaSrc = R"(
    in shader input;
    half4 main() {
        return dot(sample(input).rgb, half3(0.3, 0.6, 0.1)).000r;
    }
)";

const char* gLumaSrcWithCoords = R"(
    in shader input;
    half4 main(float2 p) {
        return dot(sample(input).rgb, half3(0.3, 0.6, 0.1)).000r;
    }
)";

// A runtime effect with a small amount of control flow (if, else, etc., and
// early return) that can in principle still be reduced to a single basic block.
// Distilled from AOSP tone mapping shaders.
const char* gComplex = R"(
    in shader input;
    half4 main() {
        half4 color = sample(input);

        half luma = dot(color.rgb, half3(0.3, 0.6, 0.1));

        half scale = 0;

        if (luma < 0.33333) {
            return half4(color.rgb * 0.5, color.a);
        } else if (luma < 0.66666) {
            scale = 0.166666 + 2.0 * (luma - 0.33333);
        } else {
            scale = 0.833333 + 0.5 * (luma - 0.66666);
        }

        return half4(color.rgb * (scale/luma), color.a);
    }
)";


DEF_SIMPLE_GM(runtimecolorfilter, canvas, 256 * 4, 256) {
    auto img = GetResourceAsImage("images/mandrill_256.png");
    canvas->drawImage(img, 0, 0, nullptr);

    for (auto src : { gLumaSrc, gLumaSrcWithCoords, gComplex }) {
        sk_sp<SkRuntimeEffect> effect = std::get<0>(SkRuntimeEffect::Make(SkString(src)));
        SkASSERT(effect);
        SkPaint p;
        sk_sp<SkColorFilter> input = nullptr;
        p.setColorFilter(effect->makeColorFilter(nullptr, &input, 1));
        canvas->translate(256, 0);
        canvas->drawImage(img, 0, 0, &p);
    }
}