BGRACompute.hpp

#pragma once
#include <Gfx/Graph/Utils.hpp>
#include <Gfx/Graph/encoders/ComputeEncoder.hpp>
#include <Gfx/Graph/encoders/GPUVideoEncoder.hpp>
 
#include <private/qrhi_p.h>
 
namespace score::gfx
{
 
struct BGRAComputeEncoder final : ComputeEncoder
{
  static constexpr const char* compute_shader = R"_(#version 450
    layout(local_size_x = 16, local_size_y = 16, local_size_z = 1) in;
 
    layout(binding = 0) uniform sampler2D src_tex;
    layout(std430, binding = 1) writeonly buffer BgraBuf {
      uint bgra[];
    };
    layout(std140, binding = 2) uniform Params {
      ivec2 src_size;
      ivec2 _pad0;
      uint  line_stride_words; // bytes-per-row / 4 == width
      uint  _pad1[3];
    };
 
    uint to_byte(float v) {
      return uint(clamp(v, 0.0, 1.0) * 255.0 + 0.5);
    }
 
    void main() {
      uint x = gl_GlobalInvocationID.x;
      uint y = gl_GlobalInvocationID.y;
      if (int(x) >= src_size.x || int(y) >= src_size.y)
        return;
 
    // See GPUVideoEncoder::y_flip_glsl: only OpenGL. The rest of the engine
    // negates Y through renderer.clipSpaceCorrMatrix on Vulkan; this pass
    // indexes texels directly and does not, so it must not flip there.
    #if defined(QSHADER_SPIRV) || defined(QSHADER_MSL) || defined(QSHADER_HLSL)
      int src_y = int(y);
    #else
      int src_y = src_size.y - 1 - int(y);
    #endif
 
      vec4 c = texelFetch(src_tex, ivec2(int(x), src_y), 0);
      uint B = to_byte(c.b);
      uint G = to_byte(c.g);
      uint R = to_byte(c.r);
      uint A = to_byte(c.a);
 
      // NTV2_FBF_ARGB byte order in memory: B, G, R, A
      uint w = B | (G << 8) | (R << 16) | (A << 24);
      bgra[y * line_stride_words + x] = w;
    }
  )_";
 
  QRhiBuffer* m_paramsUBO{};
  QRhiSampler* m_sampler{};
  QRhiShaderResourceBindings* m_srb{};
  QRhiComputePipeline* m_pipeline{};
  int m_width{};
  int m_height{};
 
  bool init(
      QRhi& rhi, const RenderState& state, QRhiTexture* inputRGBA, int width,
      int height, QRhiBuffer* outputBuffer,
      const QString& /*colorConversion*/ = colorMatrixOut()) override
  {
    if(!outputBuffer || !rhi.isFeatureSupported(QRhi::Compute))
      return false;
 
    m_width = width;
    m_height = height;
 
    m_paramsUBO = rhi.newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, 32);
    m_paramsUBO->setName("BGRAComputeEncoder::params");
    if(!m_paramsUBO->create())
      return false;
 
    m_sampler = rhi.newSampler(
        QRhiSampler::Nearest, QRhiSampler::Nearest, QRhiSampler::None,
        QRhiSampler::ClampToEdge, QRhiSampler::ClampToEdge);
    if(!m_sampler->create())
      return false;
 
    m_srb = rhi.newShaderResourceBindings();
    m_srb->setBindings({
        QRhiShaderResourceBinding::sampledTexture(
            0, QRhiShaderResourceBinding::ComputeStage, inputRGBA, m_sampler),
        QRhiShaderResourceBinding::bufferStore(
            1, QRhiShaderResourceBinding::ComputeStage, outputBuffer),
        QRhiShaderResourceBinding::uniformBuffer(
            2, QRhiShaderResourceBinding::ComputeStage, m_paramsUBO),
    });
    if(!m_srb->create())
      return false;
 
    QShader cs = makeCompute(state, QString::fromLatin1(compute_shader));
    m_pipeline = rhi.newComputePipeline();
    m_pipeline->setShaderStage({QRhiShaderStage::Compute, cs});
    m_pipeline->setShaderResourceBindings(m_srb);
    if(!m_pipeline->create())
      return false;
 
    return true;
  }
 
  void exec(
      QRhi& rhi, QRhiCommandBuffer& cb, QRhiResourceUpdateBatch* res) override
  {
    struct alignas(16) ParamsData
    {
      int32_t srcW, srcH;
      int32_t pad0[2];
      uint32_t lineStrideWords;
      uint32_t pad1[3];
    } p{m_width, m_height, {0, 0}, static_cast<uint32_t>(m_width), {0, 0, 0}};
    res->updateDynamicBuffer(m_paramsUBO, 0, sizeof(p), &p);
 
    cb.beginComputePass(res);
    cb.setComputePipeline(m_pipeline);
    cb.setShaderResources(m_srb);
    cb.dispatch((m_width + 15) / 16, (m_height + 15) / 16, 1);
    cb.endComputePass();
  }
 
  void release() override
  {
    delete m_pipeline;   m_pipeline = nullptr;
    delete m_srb;        m_srb = nullptr;
    delete m_sampler;    m_sampler = nullptr;
    delete m_paramsUBO;  m_paramsUBO = nullptr;
  }
};
 
} // namespace score::gfx