feat: only attempt to render a fixed list of image formats

lua/image/image.lua

@@ -1,6 +1,6 @@
-local utils = require("image/utils")
-local renderer = require("image/renderer")
 local magick = require("image/magick")
+local renderer = require("image/renderer")
+local utils = require("image/utils")
 
 -- { ["buf:row"]: { id, height } }
 ---@type table<string, { id: number, height: number }>
@@ -202,7 +202,7 @@ end
 ---@param path string
 ---@param options? ImageOptions
 ---@param state State
----@return Image
+---@return Image|nil
 local from_file = function(path, options, state)
   local opts = options or {}
 
@@ -214,6 +214,12 @@ local from_file = function(path, options, state)
   local absolute_path = vim.fn.fnamemodify(path, ":p")
   if not vim.loop.fs_stat(absolute_path) then utils.throw(("image.nvim: file not found: %s"):format(absolute_path)) end
 
+  -- bail if not an image
+  if not utils.magic.is_image(absolute_path) then
+    utils.debug(("image.nvim: not an image: %s"):format(absolute_path))
+    return nil
+  end
+
   -- bypass magick processing if already processed
   for _, instance in pairs(state.images) do
     if instance.original_path == absolute_path then
@@ -332,6 +338,7 @@ local from_url = function(url, options, callback, state)
         code = code,
         signal = signal,
       })
+      callback(nil)
     end
   end)
 

lua/image/init.lua

@@ -1,6 +1,6 @@
-local utils = require("image/utils")
 local image = require("image/image")
 local magick = require("image/magick")
+local utils = require("image/utils")
 
 ---@type Options
 local default_options = {
@@ -290,6 +290,7 @@ end
 ---@param win number? if nil or 0, uses current window
 ---@param buf number? if nil or 0, uses current buffer
 ---@param options ImageOptions?
+---@return Image|nil
 api.hijack_buffer = function(path, win, buf, options)
   if not win or win == 0 then win = vim.api.nvim_get_current_win() end
   if not buf or buf == 0 then buf = vim.api.nvim_get_current_buf() end
@@ -313,9 +314,12 @@ api.hijack_buffer = function(path, win, buf, options)
   opts.buffer = buf
 
   local img = api.from_file(path, opts)
-  img:render()
 
-  state.hijacked_win_buf_images[key] = img
+  if img then
+    img:render()
+    state.hijacked_win_buf_images[key] = img
+  end
+
   return img
 end
 

lua/image/utils/document.lua

@@ -104,7 +104,7 @@ local create_document_integration = function(config)
             buffer = item.window.buffer,
             with_virtual_padding = true,
           })
-          if ok then render_image(image) end
+          if ok and image then render_image(image) end
         end
       end
     end

lua/image/utils/init.lua

@@ -1,11 +1,12 @@
 local base64 = require("image/utils/base64")
 local logger = require("image/utils/logger")
-local random = require("image/utils/random")
-local window = require("image/utils/window")
-local term = require("image/utils/term")
+local magic = require("image/utils/magic")
 local math = require("image/utils/math")
 local offsets = require("image/utils/offsets")
+local random = require("image/utils/random")
+local term = require("image/utils/term")
 local tmux = require("image/utils/tmux")
+local window = require("image/utils/window")
 
 return {
   log = logger.log,
@@ -18,4 +19,5 @@ return {
   math = math,
   offsets = offsets,
   tmux = tmux,
+  magic = magic,
 }

lua/image/utils/magic.lua

@@ -0,0 +1,45 @@
+-- local log = require("image/utils/logger")
+
+local max_bytes = 9
+
+local sigs = {
+  "\x89\x50\x4E\x47", -- PNG
+  "\xFF\xD8\xFF\xE0", -- JPEG
+  "\x52\x49\x46\x46", -- WEBP
+  "\x47\x49\x46\x38", -- GIF87a, GIF89a
+  "\x42\x4D", -- BMP
+  "\x66\x74\x79\x70", -- HEIC
+  "\x2F\x2A\x20\x58\x50\x4D\x20\x2A\x2F", -- XPM
+  "\x00\x00\x01\x00", -- ICO
+}
+
+---@param path string
+---@param n? number
+local get_header = function(path, n)
+  local f = assert(io.open(path, "rb"))
+  local bytes = { f:read(n):byte(1, n) }
+  f:close()
+  return bytes
+end
+
+local is_image = function(path)
+  local header_bytes = get_header(path, max_bytes)
+  -- local header_str = string.char(unpack(header_bytes))
+  -- log.debug("signature", header_str)
+
+  for _, sig in ipairs(sigs) do
+    local match = true
+    for i = 1, #sig do
+      if header_bytes[i] ~= string.byte(sig, i) then
+        match = false
+        break
+      end
+    end
+    if match then return true end
+  end
+  return false
+end
+
+return {
+  is_image = is_image,
+}

lua/types.lua

@@ -2,7 +2,7 @@
 
 ---@class API
 ---@field setup fun(options?: Options)
----@field from_file fun(path: string, options?: ImageOptions): Image
+---@field from_file fun(path: string, options?: ImageOptions): Image|nil
 ---@field from_url fun(url: string, options?: ImageOptions, callback: fun(image: Image|nil))
 ---@field clear fun(id?: string)
 ---@field get_images fun(opts?: { window?: number, buffer?: number }): Image[]