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LibPDF: Implement SampledFunction::evaluate() for some sampled functions

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Things now work for functions that are all of:
* linear
* 1-D input
* 8 bits per sample
This commit is contained in:
Nico Weber 2023-11-05 22:13:01 +01:00 • committed by Sam Atkins
parent fd1876441a
commit 323ba7404c
1 changed files with 39 additions and 2 deletions
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41
Userland/Libraries/LibPDF/Function.cpp
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@ -40,6 +40,10 @@ private:
Vector<Bound> m_encode;
Vector<Bound> m_decode;
ReadonlyBytes m_sample_data;
Vector<float> mutable m_outputs;
};
PDFErrorOr<NonnullRefPtr<SampledFunction>>
@ -131,12 +135,45 @@ SampledFunction::create(Document* document, Vector<Bound> domain, Optional<Vecto
function->m_order = order;
function->m_encode = move(encode);
function->m_decode = move(decode);
function->m_sample_data = stream->bytes();
function->m_outputs.resize(function->m_range.size());
return function;
}
PDFErrorOr<ReadonlySpan<float>> SampledFunction::evaluate(ReadonlySpan<float>) const
PDFErrorOr<ReadonlySpan<float>> SampledFunction::evaluate(ReadonlySpan<float> x) const
{
return Error(Error::Type::RenderingUnsupported, "SampledFunction not yet implemented"_string);
if (x.size() != m_domain.size())
return Error { Error::Type::MalformedPDF, "Function argument size does not match domain size" };
if (m_order != Order::Linear)
return Error { Error::Type::RenderingUnsupported, "Sample function with cubic order not yet implemented" };
if (m_domain.size() != 1)
return Error { Error::Type::RenderingUnsupported, "Sample function with m > 1 not yet implemented" };
if (m_bits_per_sample != 8)
return Error { Error::Type::RenderingUnsupported, "Sample function with bits per sample != 8 not yet implemented" };
auto interpolate = [](float x, float x_min, float x_max, float y_min, float y_max) {
return y_min + (x - x_min) * (y_max - y_min) / (x_max - x_min);
};
float xc = clamp(x[0], m_domain[0].lower, m_domain[0].upper);
float e = interpolate(xc, m_domain[0].lower, m_domain[0].upper, m_encode[0].lower, m_encode[0].upper);
float ec = clamp(e, 0.0f, static_cast<float>(m_sizes[0] - 1));
float e0 = floor(ec);
float e1 = ceil(ec);
size_t plane_size = m_sizes[0];
for (size_t i = 0; i < m_range.size(); ++i) {
float s0 = m_sample_data[(size_t)e0 + i * plane_size];
float s1 = m_sample_data[(size_t)e1 + i * plane_size];
float r0 = interpolate(ec, e0, e1, s0, s1);
r0 = interpolate(r0, 0.0f, 255.0f, m_decode[i].lower, m_decode[i].upper);
m_outputs[i] = clamp(r0, m_range[i].lower, m_range[i].upper);
}
return m_outputs;
}
// 3.9.2 Type 2 (Exponential Interpolation) Functions