adding bitmapbackend support

Author: lisanhu

Cargo.toml

@@ -1,4 +1,3 @@
 [workspace]
 members = ["plotters", "plotters-backend", "plotters-bitmap", "plotters-svg"]
 default-members = ["plotters"]
-

plotters/src/evcxr.rs

@@ -1,6 +1,8 @@
 use crate::coord::Shift;
 use crate::drawing::{DrawingArea, IntoDrawingArea};
+use base64;
 use plotters_svg::SVGBackend;
+use plotters_bitmap::BitMapBackend;
 
 /// The wrapper for the generated SVG
 pub struct SVGWrapper(String, String);
@@ -40,3 +42,53 @@ pub fn evcxr_figure<
     draw(root).expect("Drawing failure");
     SVGWrapper(buffer, "".to_string())
 }
+
+pub struct BitmapWrapper(String, String);
+
+impl BitmapWrapper {
+    pub fn evcxr_display(&self) {
+        println!("{:?}", self);
+    }
+
+    pub fn style<S: Into<String>>(mut self, style: S) -> Self {
+        self.1 = style.into();
+        self
+    }
+}
+
+impl std::fmt::Debug for BitmapWrapper {
+    fn fmt(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+        let svg = self.0.as_str();
+        write!(
+            formatter,
+            "EVCXR_BEGIN_CONTENT text/html\n<img style=\"{}\" src=\"data:image/png;base64,{}\"/>\nEVCXR_END_CONTENT",
+            self.1, svg
+        )
+    }
+}
+
+/// Start drawing an evcxr figure
+pub fn evcxr_bitmap_figure<
+    Draw: FnOnce(DrawingArea<BitMapBackend, Shift>) -> Result<(), Box<dyn std::error::Error>>,
+>(
+    size: (u32, u32),
+    draw: Draw,
+) -> SVGWrapper {
+    let pixel_size = plotters_bitmap::bitmap_pixel::RGBPixel::PIXEL_SIZE;
+    let mut buf = [u8; (size.0 as usize) * (size.1 as usize) * pixel_size];
+    let root = BitMapBackend::with_buffer(&buf, size).into_drawing_area();
+    let buffer = base64::encode(&buf);
+    draw(root).expect("Drawing failure");
+    BitmapWrapper(buffer, "".to_string())
+}
+
+pub fn evcxr_animation<
+    Draw: FnOnce(DrawingArea<SVGBackend, Shift>) -> Result<(), Box<dyn std::error::Error>>,
+>(
+    drawing_area: &DrawingArea<SVGBackend, Shift>,
+    draws: Draw,
+    frames: usize,
+    interval: usize,
+) -> SVGWrapper {
+    todo!();
+}