LibPDF: Add scaffolding for function objects

See PDF 1.7 Spec, "3.9 Functions".

Userland/Libraries/LibPDF/CMakeLists.txt

@@ -14,6 +14,7 @@ set(SOURCES
     Fonts/Type0Font.cpp
     Fonts/Type1Font.cpp
     Fonts/Type1FontProgram.cpp
+    Function.cpp
     Interpolation.cpp
     ObjectDerivatives.cpp
     Page.cpp

Userland/Libraries/LibPDF/Function.cpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2023, Nico Weber <thakis@chromium.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibPDF/Function.h>
+
+// PDF 1.7 spec, 3.9 Functions
+
+namespace PDF {
+
+class SampledFunction final : public Function {
+public:
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const override;
+};
+
+PDFErrorOr<ReadonlySpan<float>> SampledFunction::evaluate(ReadonlySpan<float>) const
+{
+    return Error(Error::Type::RenderingUnsupported, "SampledFunction not yet implemented"_string);
+}
+
+class ExponentialInterpolationFunction final : public Function {
+public:
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const override;
+};
+
+PDFErrorOr<ReadonlySpan<float>> ExponentialInterpolationFunction::evaluate(ReadonlySpan<float>) const
+{
+    return Error(Error::Type::RenderingUnsupported, "ExponentialInterpolationFunction not yet implemented"_string);
+}
+
+class StitchingFunction final : public Function {
+public:
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const override;
+};
+
+PDFErrorOr<ReadonlySpan<float>> StitchingFunction::evaluate(ReadonlySpan<float>) const
+{
+    return Error(Error::Type::RenderingUnsupported, "StitchingFunction not yet implemented"_string);
+}
+
+class PostScriptCalculatorFunction final : public Function {
+public:
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const override;
+};
+
+PDFErrorOr<ReadonlySpan<float>> PostScriptCalculatorFunction::evaluate(ReadonlySpan<float>) const
+{
+    return Error(Error::Type::RenderingUnsupported, "PostScriptCalculatorFunction not yet implemented"_string);
+}
+
+PDFErrorOr<NonnullRefPtr<Function>> Function::create(Document*, NonnullRefPtr<Object>)
+{
+    return Error(Error::Type::RenderingUnsupported, "Function creation not yet implemented"_string);
+}
+
+}

Userland/Libraries/LibPDF/Function.h

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2023, Nico Weber <thakis@chromium.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <LibPDF/Value.h>
+
+namespace PDF {
+
+class Function : public RefCounted<Function> {
+public:
+    static PDFErrorOr<NonnullRefPtr<Function>> create(Document*, NonnullRefPtr<Object>);
+    virtual ~Function() = default;
+    virtual PDFErrorOr<ReadonlySpan<float>> evaluate(ReadonlySpan<float>) const = 0;
+};
+
+}