Add HTML support for showing images

src/ImageShow.jl

@@ -1,5 +1,6 @@
 module ImageShow
 
+import Base64
 using FileIO
 using ImageCore, OffsetArrays
 import ImageBase: restrict

src/showmime.jl

@@ -140,3 +140,29 @@ end
 
 _length1(A::AbstractArray) = length(eachindex(A))
 _length1(A) = length(A)
+
+
+
+const _HTML_IMAGE_MIMES = [
+    MIME("image/jpg"),
+    MIME("image/png"),
+]
+
+function Base.show(io::IO, ::MIME"text/html", img::ColorantMatrix)
+    _show_image_html(io, _HTML_IMAGE_MIMES, img)
+end
+
+function _show_image_html(io, mimes::Vector{<:MIME}, x)
+    for mime in _HTML_IMAGE_MIMES
+        if showable(mime, x)
+            _show_image_html(io, mime, x)
+            break
+        end
+    end
+end
+
+function _show_image_html(io, mime::MIME{Name}, x) where Name
+    buf = IOBuffer()
+    show(buf, mime, x)
+    print(io, """<img src="data:""", Name, ";base64,", Base64.base64encode(take!(buf)), "\" />")
+end

test/writemime.jl

@@ -153,6 +153,15 @@ end
         end
         @test load(fn) == A[[1,1,2,2],[1,1,2,2]]
     end
+    @testset "HTML display" begin
+        sshow(mime, x) = (io = IOBuffer(); show(io, mime, x); String(take!(io)))
+        @test startswith(
+            sshow(MIME("text/html"), zeros(Gray{Float32}, 1, 1)),
+            "<img src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAGQAAABkCAAAAABV")
+        @test startswith(
+            sshow(MIME("text/html"), zeros(RGB{Float32}, 1, 1)),
+            "<img src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAGQAAABkCAIAAAD/")
+    end
 end
 try
     # if this fails, it is not our fault