add support to display PNG for arbitrary types (#76)

Author: jwortmann

src/display.jl

@@ -4,7 +4,17 @@ struct TerminalGraphicDisplay{TC<:IO,TS<:IO} <: AbstractDisplay
 end
 TerminalGraphicDisplay(io::IO) = TerminalGraphicDisplay(io, io)
 
-Base.displayable(::TerminalGraphicDisplay, ::MIME"image/png") = true
+Base.displayable(::TerminalGraphicDisplay, ::MIME"image/png", x::Any) =
+    showable("image/png", x)
+Base.displayable(::TerminalGraphicDisplay, ::MIME"image/png", ::Vector{UInt8}) = true
+Base.displayable(::TerminalGraphicDisplay, ::MIME"image/png", ::AbstractArray{<:Colorant}) =
+    true
+
+function Base.display(d::TerminalGraphicDisplay, ::MIME"image/png", x::Any)
+    io = IOBuffer()
+    show(io, "image/png", x)
+    display(d, MIME("image/png"), FileIO.load(io))
+end
 
 function Base.display(d::TerminalGraphicDisplay, ::MIME"image/png", bytes::Vector{UInt8})
     # In this case, assume it to be png byte sequences, use FileIO to find a decoder for it.

test/tst_display.jl

@@ -15,4 +15,11 @@
     dsp = ImageInTerminal.TerminalGraphicDisplay(io)
     display(dsp, MIME("image/png"), bytes)
     @test length(read(io, String)) > 5_000
+
+    struct Foo end
+    Base.show(io::IO, ::MIME"image/png", ::Foo) =
+        FileIO.save(Stream{format"PNG"}(io), FileIO.load(fn))
+    dsp = ImageInTerminal.TerminalGraphicDisplay(io)
+    display(dsp, MIME("image/png"), Foo())
+    @test length(read(io, String)) > 5_000
 end