There is an open Issue 2441 requesting the ability to append gmail signatures to email when using the GMailService. Visit and star it to receive updates.
As @wchiquito suggests, you can craft a script to attach images, producing a signature. You can also use HTML tags such as <B></B>
to render text in bold, and so on.
Here's a different approach that will instead use a draft email as a template. This way, you can produce your signature with a variety of fonts and images using the online editor, and end up with a capability similar to automatic signature insertion.
The template needs to be saved in your Drafts folder, and it needs to have a tag indicating where the body of emails should go.
Example
function sendWithTemplate() {
var msgBody = "Test of sending a message using a template with a signature.";
sendGmailTemplate(Session.getActiveUser().getEmail(), 'test', msgBody );
}
Script
/**
* Insert the given email body text into an email template, and send
* it to the indicated recipient. The template is a draft message with
* the subject "TEMPLATE"; if the template message is not found, an
* exception will be thrown. The template must contain text indicating
* where email content should be placed: {BODY}.
*
* @param {String} recipient Email address to send message to.
* @param {String} subject Subject line for email.
* @param {String} body Email content, may be plain text or HTML.
* @param {Object} options (optional) Options as supported by GmailApp.
*
* @returns GmailApp the Gmail service, useful for chaining
*/
function sendGmailTemplate(recipient, subject, body, options) {
options = options || {}; // default is no options
var drafts = GmailApp.getDraftMessages();
var found = false;
for (var i=0; i<drafts.length && !found; i++) {
if (drafts[i].getSubject() == "TEMPLATE") {
found = true;
var template = drafts[i];
}
}
if (!found) throw new Error( "TEMPLATE not found in drafts folder" );
// Generate htmlBody from template, with provided text body
var imgUpdates = updateInlineImages(template);
options.htmlBody = imgUpdates.templateBody.replace('{BODY}', body);
options.attachments = imgUpdates.attachments;
options.inlineImages = imgUpdates.inlineImages;
return GmailApp.sendEmail(recipient, subject, body, options);
}
/**
* This function was adapted from YetAnotherMailMerge by Romain Vaillard.
* Given a template email message, identify any attachments that are used
* as inline images in the message, and move them from the attachments list
* to the inlineImages list, updating the body of the message accordingly.
*
* @param {GmailMessage} template Message to use as template
* @returns {Object} An object containing the updated
* templateBody, attachments and inlineImages.
*/
function updateInlineImages(template) {
//////////////////////////////////////////////////////////////////////////////
// Get inline images and make sure they stay as inline images
//////////////////////////////////////////////////////////////////////////////
var templateBody = template.getBody();
var rawContent = template.getRawContent();
var attachments = template.getAttachments();
var regMessageId = new RegExp(template.getId(), "g");
if (templateBody.match(regMessageId) != null) {
var inlineImages = {};
var nbrOfImg = templateBody.match(regMessageId).length;
var imgVars = templateBody.match(/<img[^>]+>/g);
var imgToReplace = [];
if(imgVars != null){
for (var i = 0; i < imgVars.length; i++) {
if (imgVars[i].search(regMessageId) != -1) {
var id = imgVars[i].match(/realattid=([^&]+)&/);
if (id != null) {
var temp = rawContent.split(id[1])[1];
temp = temp.substr(temp.lastIndexOf('Content-Type'));
var imgTitle = temp.match(/name="([^"]+)"/);
if (imgTitle != null) imgToReplace.push([imgTitle[1], imgVars[i], id[1]]);
}
}
}
}
for (var i = 0; i < imgToReplace.length; i++) {
for (var j = 0; j < attachments.length; j++) {
if(attachments[j].getName() == imgToReplace[i][0]) {
inlineImages[imgToReplace[i][2]] = attachments[j].copyBlob();
attachments.splice(j, 1);
var newImg = imgToReplace[i][1].replace(/src="[^"]+"/, "src="cid:" + imgToReplace[i][2] + """);
templateBody = templateBody.replace(imgToReplace[i][1], newImg);
}
}
}
}
var updatedTemplate = {
templateBody: templateBody,
attachments: attachments,
inlineImages: inlineImages
}
return updatedTemplate;
}
Credit where credit is due: The "Yet Another Mail Merge" script includes code that preserves inline images in emails during a mail merge - I've borrowed from that. Thanks Romain!