{
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{
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"source": [
"# greyscale\n",
"\n",
"\n",
"\n",
"\n",
"**Author:** Olivier Couet \n",
"This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, May 19, 2026 at 08:37 PM."
]
},
{
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"id": "ff42997b",
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"source": [
"TCanvas *c = new TCanvas(\"grey\", \"Grey Scale\", 500, 500);\n",
"c->SetBorderMode(0);\n",
"\n",
"Int_t n = 200; // tunable parameter\n",
"Float_t n1 = 1. / n;\n",
"for (int i = 0; i < n; i++) {\n",
" for (int j = 0; j < n; j++) {\n",
" TBox *b = new TBox(n1 * j, n1 * (n - 1 - i), n1 * (j + 1), n1 * (n - i));\n",
" Float_t grey = Float_t(i * n + j) / (n * n);\n",
" b->SetFillColor(TColor::GetColor(grey, grey, grey));\n",
" b->Draw();\n",
" }\n",
"}\n",
"TPad *p = new TPad(\"p\", \"p\", 0.3, 0.3, 0.7, 0.7);\n",
"const char *guibackground = gEnv->GetValue(\"Gui.BackgroundColor\", \"\");\n",
"p->SetFillColor(TColor::GetColor(guibackground));\n",
"p->Draw();\n",
"p->cd();\n",
"TText *t = new TText(0.5, 0.5, \"GUI Background Color\");\n",
"t->SetTextAlign(22);\n",
"t->SetTextSize(.09);\n",
"t->Draw();\n",
"\n",
"c->SetEditable(kFALSE);"
]
},
{
"cell_type": "markdown",
"id": "6ffbe693",
"metadata": {},
"source": [
"Draw all canvases "
]
},
{
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"execution_count": 2,
"id": "f84ac0a8",
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"shell.execute_reply": "2026-05-19T20:37:11.671393Z"
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"outputs": [
{
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],
"source": [
"gROOT->GetListOfCanvases()->Draw()"
]
}
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"language": "c++",
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