Lua

Get the Content-ID of a Related Item

Demonstrates the Chilkat Email.GetRelatedContentID method, which returns the Content-ID of a related item (typically an image or style sheet embedded within an HTML email). The index is zero-based. This example loads an image from a file into a BinData object, adds it as a related item with AddRelatedBd (capturing the generated Content-ID and referencing it from the HTML), then reads that Content-ID back.

Background: The Content-ID is the anchor that ties an inline resource to the HTML that displays it: the body references cid: plus the ID, and the matching related part carries that same Content-ID. Because an image is binary, it is loaded into a BinData object (here from a file) and added with AddRelatedBd. Reading the Content-ID back lets a program verify or rewrite those links — for example when relocating embedded images or converting a message for display outside a mail client.

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Lua

local chilkat = require("chilkat")

-- Demonstrates the GetRelatedContentID method, which returns the Content-ID of a related
-- item.  Related items are typically images and style sheets embedded within HTML emails.
-- The index is zero-based.

local email = chilkat.Email.new()
email.subject = "GetRelatedContentID example"

-- Load the image data from a file into a BinData object.
local bdImage = chilkat.BinData.new()
local success = bdImage:load_file("qa_data/images/logo.png")
if not success then
    print(bdImage.last_error_text)
    return
end

-- Add the image as a related item from the BinData; capture its generated Content-ID.
local cid = email:add_related_bd("logo.png", bdImage)
if not email.last_method_success then
    print(email.last_error_text)
    return
end

-- Reference the related item in the HTML body by its Content-ID.
local sbHtml = chilkat.StringBuilder.new()
sbHtml:append("<html><body><img src=\"cid:PLACEHOLDER_CID\"/></body></html>")
local numReplaced = sbHtml:replace("PLACEHOLDER_CID", cid)
email:set_html_body(sbHtml:get_as_string())

-- Read the Content-ID of the first related item (index 0).
local cid0 = email:get_related_content_id(0)
print("Related item 0 Content-ID: " .. cid0)

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