Add saving plot as tiff (#591)

crates/amalthea/src/comm/plot_comm.rs

@@ -64,7 +64,11 @@ pub enum RenderFormat {
 
 	#[serde(rename = "pdf")]
 	#[strum(to_string = "pdf")]
-	Pdf
+	Pdf,
+
+	#[serde(rename = "tiff")]
+	#[strum(to_string = "tiff")]
+	Tiff
 }
 
 /// Possible values for PlotUnit

crates/amalthea/src/comm/ui_comm.rs

@@ -466,6 +466,12 @@ pub enum UiFrontendEvent {
 	#[serde(rename = "show_html_file")]
 	ShowHtmlFile(ShowHtmlFileParams),
 
+	/// This event is used to signal that the stored messages the front-end
+	/// replays when constructing multi-output plots should be reset. This
+	/// happens for things like a holoviews extension being changed.
+	#[serde(rename = "clear_webview_preloads")]
+	ClearWebviewPreloads,
+
 }
 
 /**

crates/ark/src/modules/positron/graphics.R

@@ -57,6 +57,12 @@ renderWithPlotDevice <- function(filepath, format, width, height, res, type ) {
             res      = res,
             type     = type
         ),
+        "tiff" = grDevices::tiff(
+            filename = filepath,
+            width    = width,
+            height   = height,
+            type     = type
+        ),
         stop("Internal error: Unknown plot `format`.")
     )
 }

crates/ark/src/plots/graphics_device.rs

@@ -220,6 +220,7 @@ impl DeviceContext {
             RenderFormat::Svg => "image/svg+xml".to_string(),
             RenderFormat::Pdf => "application/pdf".to_string(),
             RenderFormat::Jpeg => "image/jpeg".to_string(),
+            RenderFormat::Tiff => "image/tiff".to_string(),
         }
     }