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Add native PNG backend and fallback-first example rendering path
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10 files changed

+499
-36
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10 files changed

+499
-36
lines changed

‎CMakeLists.txt‎

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Original file line numberDiff line numberDiff line change
@@ -23,6 +23,7 @@ add_library(gnuplotpp
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src/gnuplot_backend.cpp
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src/presets.cpp
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src/svg_backend.cpp
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src/png_backend.cpp
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)
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add_library(gnuplotpp::gnuplotpp ALIAS gnuplotpp)
@@ -79,4 +80,8 @@ if(BUILD_TESTING)
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add_executable(gnuplotpp_svg_backend_test tests/svg_backend_test.cpp)
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target_link_libraries(gnuplotpp_svg_backend_test PRIVATE gnuplotpp::gnuplotpp)
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add_test(NAME gnuplotpp_svg_backend_test COMMAND gnuplotpp_svg_backend_test)
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add_executable(gnuplotpp_png_backend_test tests/png_backend_test.cpp)
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target_link_libraries(gnuplotpp_png_backend_test PRIVATE gnuplotpp::gnuplotpp)
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add_test(NAME gnuplotpp_png_backend_test COMMAND gnuplotpp_png_backend_test)
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endif()

‎README.md‎

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Original file line numberDiff line numberDiff line change
@@ -18,10 +18,12 @@ flowchart LR
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B --> C[IPlotBackend]
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C --> D[GnuplotBackend]
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C --> E[SvgBackend]
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C --> J[PngBackend]
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D --> F[tmp/*.dat]
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D --> G[tmp/figure.gp]
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D --> H[figure.pdf|svg|eps|png]
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E --> I[figure.svg]
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J --> K[figure.png]
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```
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## Render Flow
@@ -74,7 +76,8 @@ If network/package resolution fails, configuration now degrades with warnings an
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You run only the C++ executable.
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- If `gnuplot` exists, examples render publication outputs (`pdf/svg/png`) via `GnuplotBackend`.
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- If `gnuplot` is missing, examples automatically fall back to native `SvgBackend` and still generate `figure.svg`.
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- If `gnuplot` is missing, examples automatically fall back to native `PngBackend` and generate `figure.png`.
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- If PNG fallback fails, examples try native `SvgBackend` as a secondary fallback.
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## Example Plots
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@@ -85,4 +88,4 @@ You run only the C++ executable.
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Generated outputs include at least:
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- `out/<name>/figures/figure.svg`
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- `out/<name>/figures/figure.png`

‎examples/layout_2x2_example.cpp‎

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Original file line numberDiff line numberDiff line change
@@ -1,4 +1,5 @@
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#include "gnuplotpp/gnuplot_backend.hpp"
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#include "gnuplotpp/png_backend.hpp"
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#include "gnuplotpp/plot.hpp"
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#include "gnuplotpp/presets.hpp"
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#include "gnuplotpp/svg_backend.hpp"
@@ -72,16 +73,24 @@ int main(int argc, char** argv) {
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fig.axes(2).add_series(SeriesSpec{.type = SeriesType::Line, .label = "SRIF"}, t, ez);
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fig.axes(3).add_series(SeriesSpec{.type = SeriesType::Line, .label = "SRIF"}, t, ev);
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RenderResult result;
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if (gnuplot_available()) {
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fig.set_backend(make_gnuplot_backend());
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result = fig.save(out_dir / "figures");
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} else {
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fig.set_backend(make_svg_backend());
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fig.set_backend(make_png_backend());
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result = fig.save(out_dir / "figures");
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if (!result.ok) {
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fig.set_backend(make_svg_backend());
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result = fig.save(out_dir / "figures");
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}
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}
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const auto result = fig.save(out_dir / "figures");
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if (!result.ok) {
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std::cerr << "plot render incomplete: " << result.message << "\n";
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std::cerr << "script: " << result.script_path << "\n";
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if (!result.script_path.empty()) {
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std::cerr << "script: " << result.script_path << "\n";
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}
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return 1;
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}
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‎examples/two_window_example.cpp‎

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@@ -1,4 +1,5 @@
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#include "gnuplotpp/gnuplot_backend.hpp"
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#include "gnuplotpp/png_backend.hpp"
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#include "gnuplotpp/plot.hpp"
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#include "gnuplotpp/presets.hpp"
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#include "gnuplotpp/svg_backend.hpp"
@@ -64,15 +65,24 @@ int main(int argc, char** argv) {
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fig.axes(0, 0).add_series(SeriesSpec{.type = SeriesType::Line, .label = "SRIF"}, t, ep);
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fig.axes(0, 1).add_series(SeriesSpec{.type = SeriesType::Line, .label = "SRIF"}, t, ev);
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RenderResult result;
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if (gnuplot_available()) {
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fig.set_backend(make_gnuplot_backend());
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} else { fig.set_backend(make_svg_backend());
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result = fig.save(out_dir / "figures");
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} else {
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fig.set_backend(make_png_backend());
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result = fig.save(out_dir / "figures");
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if (!result.ok) {
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fig.set_backend(make_svg_backend());
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result = fig.save(out_dir / "figures");
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}
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}
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const auto result = fig.save(out_dir / "figures");
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if (!result.ok) {
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std::cerr << "plot render incomplete: " << result.message << "\n";
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std::cerr << "script: " << result.script_path << "\n";
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if (!result.script_path.empty()) {
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std::cerr << "script: " << result.script_path << "\n";
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}
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return 1;
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}
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‎include/gnuplotpp/png_backend.hpp‎

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#pragma once
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#include "gnuplotpp/plot.hpp"
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#include <memory>
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namespace gnuplotpp {
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/**
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* @brief Native C++ PNG renderer backend.
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*/
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class PngBackend final : public IPlotBackend {
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public:
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/**
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* @brief Render figure content directly to PNG output.
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* @param fig Figure to render.
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* @param out_dir Output directory.
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* @return Render status and generated paths.
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*/
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RenderResult render(const Figure& fig,
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const std::filesystem::path& out_dir) override;
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};
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/** @brief Factory helper for native PNG backend. */
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std::shared_ptr<IPlotBackend> make_png_backend();
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} // namespace gnuplotpp

‎include/gnuplotpp/svg_backend.hpp‎

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@@ -7,7 +7,7 @@
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namespace gnuplotpp {
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/**
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* @brief Native C++ SVG renderer backend (no external plotting command).
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* @brief Native C++ SVG renderer backend.
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*/
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class SvgBackend final : public IPlotBackend {
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public:

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