Library
Module
Module type
Parameter
Class
Class type
The following examples show for each renderer the minimal code and compilation instructions needed to output an image.
Other examples of images and their source can be found in the online version of Vg's test image database. Clicking on the title of an image brings you to its definition.
This example produces a one-page PDF document. Step by step we have:
Vgr_pdf
renderer on a given output channel. This function defines some metadata for the image, a function to print rendering warnings and then renders the image.stdout
in binary mode to avoid any unhelpful surprises and render the image on it.cat << 'EOF' > min_pdf.ml
open Gg
open Vg
(* 1. Define your image *)
let aspect = 1.618
let size = Size2.v (aspect *. 100.) 100. (* mm *)
let view = Box2.v P2.o (Size2.v aspect 1.)
let image = I.const (Color.v_srgb 0.314 0.784 0.471)
(* 2. Render *)
let render oc =
let title = "Vgr_pdf minimal example" in
let description = "Emerald Color" in
let xmp = Vgr.xmp ~title ~description () in
let warn w = Vgr.pp_warning Format.err_formatter w in
let r = Vgr.create ~warn (Vgr_pdf.target ~xmp ()) (`Channel oc) in
ignore (Vgr.render r (`Image (size, view, image)));
ignore (Vgr.render r `End)
(* 3. Main *)
let main () = Out_channel.set_binary_mode stdout true; render stdout; 0
let () = if !Sys.interactive then () else exit (main ())
EOF
The source can be compiled an executed with:
ocamlfind ocamlopt -package gg,vg,vg.pdf -linkpkg min_pdf.ml ./a.out > min.pdf
This example produces an SVG image. Step by step we have:
Vgr_svg
renderer on a given output channel. This function defines some metadata for the image, a function to print rendering warnings and then renders the image.stdout
in binary mode to avoid any unhelpful surprises and render the image on it.cat << 'EOF' > min_svg.ml
open Gg
open Vg
(* 1. Define your image *)
let aspect = 1.618
let size = Size2.v (aspect *. 100.) 100. (* mm *)
let view = Box2.v P2.o (Size2.v aspect 1.)
let image = I.const (Color.v_srgb 0.314 0.784 0.471)
(* 2. Render *)
let render oc =
let title = "Vgr_svg minimal example" in
let description = "Emerald Color" in
let xmp = Vgr.xmp ~title ~description () in
let warn w = Vgr.pp_warning Format.err_formatter w in
let r = Vgr.create ~warn (Vgr_svg.target ~xmp ()) (`Channel oc) in
ignore (Vgr.render r (`Image (size, view, image)));
ignore (Vgr.render r `End)
(* 3. Main *)
let main () = Out_channel.set_binary_mode stdout true; render stdout; 0
let () = if !Sys.interactive then () else exit (main ())
EOF
The source can be compiled and executed with:
ocamlfind ocamlopt -package gg,vg,vg.svg -linkpkg min_svg.ml ./a.out > min.svg
This example produces a web page with an HTML canvas image. It uses the Brr
library to interact with the browser. Step by step we have:
cnv
.anchor
that parents cnv
. This allows to download a (usually PNG) file of the image by clicking on it.r
targeting the canvas cnv
.cat << 'EOF' > min_htmlc.ml
open Gg
open Vg
open Brr
open Brr_canvas
(* 1. Define your image *)
let aspect = 1.618
let size = Size2.v (aspect *. 100.) 100. (* mm *)
let view = Box2.v P2.o (Size2.v aspect 1.)
let image = I.const (Color.v_srgb 0.314 0.784 0.471)
(* Browser bureaucracy. *)
let main () =
let cnv = Brr_canvas.Canvas.create [] (* 2 *) in
let anchor = (* 3 *)
let href = At.href (Jstr.v "#") in
let title = At.title (Jstr.v "Download PNG file") in
let download = At.v (Jstr.v "download") (Jstr.v "min_htmlc.png") in
let a = El.a ~at:[href; title; download] [Brr_canvas.Canvas.to_el cnv] in
El.append_children (Document.body G.document) [a]; a
in
let r = Vgr.create (Vgr_htmlc.target cnv) `Other in (* 4 *)
ignore (Vgr.render r (`Image (size, view, image))); (* 5 *)
ignore (Vgr.render r `End);
let data = (* 6 *)
Canvas.to_data_url cnv |> Console.log_if_error ~use:Jstr.empty
in
El.set_at At.Name.href (Some data) anchor
let () = main () (* 7 *)
EOF
The source needs to be compiled to bytecode and then to JavaScript with js_of_ocaml
:
ocamlfind ocamlc -package brr,gg,vg,vg.htmlc -linkpkg min_htmlc.ml js_of_ocaml -o min_htmlc.js a.out
Finally we need to link that with a minimal HTML file. The following one will do:
cat << 'EOF' > min_htmlc.html <!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width,initial-scale=1.0"> <script type="text/javascript" defer="defer" src="min_htmlc.js"></script> <style type="text/css"> body { background-color: black; margin: 3em; } </style> <title>Vgr_htmlc minimal example</title> </head> <body> <noscript>Sorry, you need to enable JavaScript to see this page.</noscript> </body> </html> EOF
You can now enjoy your image by invoking:
xdg-open min_htmlc.html # Linux and XDG compliant systems open min_htmlc.html # macOS start min_htmlc.html # Windows
This example produces a PNG image with Cairo. Step by step we have:
Vgr_cairo
renderer on a given output channel. This function defines the output format, a function to print rendering warnings and then renders the image.stdout
in binary mode to avoid any unhelpful surprises and render the image on it.cat << 'EOF' > min_cairo_png.ml
open Gg
open Vg
(* 1. Define your image *)
let aspect = 1.618
let size = Size2.v (aspect *. 100.) 100. (* mm *)
let view = Box2.v P2.o (Size2.v aspect 1.)
let image = I.const (Color.v_srgb 0.314 0.784 0.471)
(* 2. Render *)
let render oc =
let res = 300. /. 0.0254 (* 300dpi in dots per meters *) in
let format = `Png (Size2.v res res) in
let warn w = Vgr.pp_warning Format.err_formatter w in
let r = Vgr.create ~warn (Vgr_cairo.stored_target format) (`Channel oc) in
ignore (Vgr.render r (`Image (size, view, image)));
ignore (Vgr.render r `End)
(* 3. Main *)
let main () = Out_channel.set_binary_mode stdout true; render stdout; 0
let () = if !Sys.interactive then () else exit (main ())
EOF
The source can be compiled an executed with:
ocamlfind ocamlopt -package gg,vg,vg.cairo -linkpkg min_cairo_png.ml ./a.out > min.png
This example produces a raster image in memory with Cairo. Step by step we have:
cat << 'EOF' > min_cairo_mem.ml
open Gg
open Vg
(* 1. Define your image *)
let aspect = 1.618
let size = Size2.v (aspect *. 100.) 100. (* mm *)
let view = Box2.v P2.o (Size2.v aspect 1.)
let image = I.const (Color.v_srgb 0.314 0.784 0.471)
(* 2. Render *)
let raster, stride =
let res = 300. /. 25.4 (* 300dpi in dots per mm *) in
let w = int_of_float (res *. Size2.w size) in
let h = int_of_float (res *. Size2.h size) in
let stride = Cairo.Image.(stride_for_width ARGB32 w) in
let data = Bigarray.(Array1.create int8_unsigned c_layout (stride * h)) in
let surface = Cairo.Image.(create_for_data8 data ARGB32 ~stride ~w ~h) in
let ctx = Cairo.create surface in
Cairo.scale ctx res res;
let warn w = Vgr.pp_warning Format.err_formatter w in
let r = Vgr.create ~warn (Vgr_cairo.target ctx) `Other in
ignore (Vgr.render r (`Image (size, view, image)));
ignore (Vgr.render r `End);
Cairo.Surface.flush surface;
Cairo.Surface.finish surface;
data, stride
EOF
This example can be compiled with:
ocamlfind ocamlopt -package cairo2,gg,vg,vg.cairo -linkpkg min_cairo_mem.ml