So I have this doubt. I already have code that works with local (embedded) image files, but now I need to load an external image instead. Dumb replacing with loadImageExt didn't help:
productImageIO :: IO (Diagram B)
productImageIO = do
res <- loadImageExt "https://s7d2.scene7.com/is/image/dkscdn/16JDNMJRDNCLPSBLKJRD_Black_Black_White_is/"
return $
case res of
Left err -> mempty
Right product -> image product
• No instance for (Renderable (DImage Double External) B)
arising from a use of ‘image’
• In the expression: image product
In a case alternative: Right product -> image product
In the second argument of ‘($)’, namely
‘case res of
Left err -> mempty
Right product -> image product’
|
26 | Right product -> image product
| ^^^^^^^^^^^^^
Looking at the source of loadImageExt and readImage I cannot see where it actually performs http stuff to get the image.
And the docs say, loadImageExt, Check that a file exists, and use JuicyPixels to figure out the right size, but save a reference to the image instead of the raster data
So please excuse my ignorance, but does this mean that I need to add http loading logic in this case? Or I'm just missing some point to make this work?
UPD: I might be wrong and there's some fast and easy way to load external images by just putting the link, but what worked for me was using http-conduit, getting the response in ByteString and parsing it:
productImageIO :: String -> IO (Diagram B)
productImageIO path = do
response <- fmap getResponseBody $ parseRequest path >>= httpBS
return $
case loadImageEmbBS response of
Left error -> mempty
Right decodedImage -> image decodedImage
It could load even https image, like this https://sneakernews.com/wp-content/uploads/2018/01/jordan-russell-westbrook-signature-shoe-creamsicle-3.jpg?w=1140
loadImageExt appears to expect a FilePath, not a URL, but that's not what the compiler is complaining about. It is complaining that the particular image returned, a DImage Double External, is not Renderable. This could be because the renderer in use doesn't understand external images; for instance, Diagrams.Backend.SVG appears to support Embedded but not External. In contrast, Diagrams.Backend.Html5 supports External but not Embedded. At a guess, it's expected that your diagram refers using local filenames to images, not cross-site URLs. It could be that you can inject URLs with uncheckedImageRef, but still only if the backend supports External. The Diagrams manual section on images claims only the Cairo backend does, but that could be inaccurate.
