Lua

Add a Related File to an HTML Email

Demonstrates the Chilkat Email.AddRelatedFile method, which adds the contents of a local file as a related MIME resource and returns the generated Content-ID. The returned value is the bare Content-ID — no angle brackets and no cid: prefix — so if it returns CID-123@example, the HTML reference is cid:CID-123@example. Because the Content-ID is generated by the call, this example adds the image first, then builds the HTML body in a StringBuilder — using a placeholder in the <img> tag that is replaced with the returned Content-ID — and passes the result to SetHtmlBody.

Background: To embed an image so it displays inside an HTML email (rather than being downloaded from a web server), you add it as a "related" part and reference it from the HTML with a cid: URL that matches the part's Content-ID. Since Chilkat assigns that ID when you add the file, the natural order is: add the related file, capture the returned ID, then build the <img src="cid:..."> reference from it. A StringBuilder makes assembling and updating the HTML convenient.

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Lua

local chilkat = require("chilkat")

-- Demonstrates the AddRelatedFile method, which adds a local file as a related MIME
-- resource (such as an image displayed by an HTML body) and returns the generated
-- Content-ID.  The HTML references the item using cid:<Content-ID>.

local email = chilkat.Email.new()
email.subject = "Email with a related image"

-- Add the image file as a related item first.  The return value is the bare Content-ID
-- (no angle brackets and no "cid:" prefix).
local cid = email:add_related_file("qa_data/images/logo.png")
if not email.last_method_success then
    print(email.last_error_text)
    return
end

-- Build the HTML body in a StringBuilder, using a placeholder where the image's
-- Content-ID will go.
local sbHtml = chilkat.StringBuilder.new()
sbHtml:append("<html><body><img src=\"cid:PLACEHOLDER_CID\"/></body></html>")

-- Replace the placeholder with the actual Content-ID returned by AddRelatedFile.
local numReplaced = sbHtml:replace("PLACEHOLDER_CID", cid)

-- Set the HTML body from the StringBuilder result.
email:set_html_body(sbHtml:get_as_string())

print("Related Content-ID = " .. cid)
print("NumRelatedItems = " .. email.num_related_items)

-- Note: The path "qa_data/images/logo.png" is a relative local filesystem path,
-- relative to the current working directory of the running application.