CANU – Canvas UNIfier for ROOT

CANU (CANvas UNIfier) is a lightweight C++17 header-only library utility for the ROOT framework that helps produce publication‑ready, consistently formatted plots. It solves common issues in ROOT graphics related to canvas sizes, font scaling, axis formatting, margins, and legend placement.

Designed for high‑energy physics analysis and journal publication workflows (e.g. EPJC, PRC, NIM, etc.).

It will transform your paper into a polished, consistently professional piece of writing.:

None-formatted output	CANU-formatted plots

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📌 Features

• 📐 Canvas sizing tools
  Resize canvases to true physical sizes with consistent aspect ratio.

• 🔠 Font & axis formatting
  Uniform font sizes in points, axis division/offset control.

• 📊 Legend utilities
  Automatic placement and sizing of TLegend boxes.

• 📏 Margins & layout helpers
  Normalization of margins with reference to page width.

• 🧰 Journal presets
  Ready‑to‑use formatting for EPJC, NIM, PRC.

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🚀 Quick Start

Requirements

• ROOT (≥ 6.x)
• C++17 compiler

Installation

CANU is header‑only — just include the header in your project:

#include "canu/canu.hpp"

And compile with:

g++ my_analysis.cpp $(root-config --cflags --libs)

or add to your cmake

find_package(canu REQUIRED)

target_link_libraries(project_exe PRIVATE canu::canu)

🧠 Basic Usage

Create a CANU formatter

There are built‑in presets for common publication formats:

auto canu = cu::make_epjc_paper();

Resize a ROOT canvas

TCanvas c("c", "Plot", 800, 600);

hist->Draw();

canu.make_page_wide(&c);
c.SaveAs("figure.pdf");

This resizes the canvas to page width, applies fonts and margins.

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🧰 API Reference

Canvas Sizing

Method	Description
resize_canvas(can, w, h)	Resize to arbitrary width/height
make_page_wide(can)	Resize to page width
make_column_wide(can)	Resize to standard column width

Axis Properties

Method	Description
set_max_digits(n)	Maximum number of digits on axis
set_ndivisions(n)	Number of axis divisions
set_title_offset(f)	Title offset
set_label_offset(f)	Label offset

Legends

Method	Description
place_legend(x, y, rows, cols, width)	Creates a TLegend
format_legend(can)	Formats all legends in canvas

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🧪 Examples

Formatting Existing ROOT Macros

Prepare macros to make page (_canu_2d_page.C):

#include "canu.hpp"

void _canu_2d_page(const char * macro_name)
{
    gStyle->SetPalette(kBird);

    auto canu = cu::make_nim_paper();
    canu.set_details_scale(2);

    gROOT->ProcessLine(Form(".x %s", macro_name));

    canu.make_page_wide(gPad->GetCanvas());
    canu.format_legend(gPad->GetCanvas());

    TString fname = macro_name;
    fname.ReplaceAll(".C", "");

    gPad->SaveAs(Form("out/%s.pdf", basename(fname.Data())));
    gPad->SaveAs(Form("out/%s.png", basename(fname.Data())));
    gPad->SaveAs(Form("out/%s.C", basename(fname.Data())));
}

and column-wide formatter (_canu_2d_column.C):

#include "canu.hpp"

void _canu_2d_column(const char * macro_name)
{
    gStyle->SetPalette(kBird);

    auto canu = cu::make_nim_paper();
    canu.set_details_scale(2);

    gROOT->ProcessLine(Form(".x %s", macro_name));

    canu.make_column_wide(gPad->GetCanvas());
    canu.format_legend(gPad->GetCanvas());

    TString fname = macro_name;
    fname.ReplaceAll(".C", "");

    gPad->SaveAs(Form("out/%s.pdf", basename(fname.Data())));
    gPad->SaveAs(Form("out/%s.png", basename(fname.Data())));
    gPad->SaveAs(Form("out/%s.C", basename(fname.Data())));
}

(these two differ by make_page_wide and make_column_wide only).

Prepare wrapper scripts: wrapper_canu_page.sh

#!/bin/bash

mkdir -p out
for f in $@; do
    root -l _canu_2d_page.C\(\"$f\"\) -q -b
done

and wrapper_canu_column.sh

#!/bin/bash

mkdir -p out
for f in $@; do
    root -l _canu_2d_column.C\(\"$f\"\) -q -b
done

Now, all your plots supposed for page-wide display format with:

./wrapper_canu_page.sh plot1.C plot2.C

and for column-wide plots:

./wrapper_canu_column.sh plot3.C plot4.C

See example/ directory for working examples. Use make or build_examples.sh. Example can be used as a base for your paper workflow.

Histogram Formatting

void plot1() {
    TH1F h("h","Example",100,-3,3);
    h.FillRandom("gaus",10000);

    TCanvas c("c","c",800,600);
    h.Draw();

    auto canu = cu::make_epjc_paper();
    canu.make_column_wide(&c);

    c.SaveAs("hist_column.pdf");
}

Overlay with Axis Control

void plot_overlay() {
    TH1F h1("h1","Data",100,-5,5);
    TH1F h2("h2","Model",100,-5,5);

    h1.SetLineColor(kBlue);
    h2.SetLineColor(kRed);

    TCanvas c("c","Overlay",800,600);
    h1.Draw();
    h2.Draw("same");

    auto canu = cu::make_prc_paper();
    canu.x_prop().set_ndivisions(510);
    canu.y_prop().set_ndivisions(505);

    canu.make_page_wide(&c);

    c.SaveAs("overlay_prc.pdf");
}

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⚠️ Common ROOT Pitfalls Solved by CANU

• Batch mode window/canvas size inconsistencies
• Incorrect font scaling in points
• Inconsistent margins across different canvases
• Axis label offsets and legend sizing issues

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📦 Journal Presets

auto epjc = cu::make_epjc_paper();
auto nim  = cu::make_nim_paper();
auto prc  = cu::make_prc_paper();

To request other journals, create new issue or submit new Pull request. See example how to prepare new journal definition.

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Building and installing

See the BUILDING document.

🧑‍💻 Contributing

See the CONTRIBUTING document. Pull requests are welcome.

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📄 License

GPL-3.0 — see LICENSE.