joplin/ReactNativeClient/lib/renderers/MdToHtml/rules/html_image.js

const Entities = require('html-entities').AllHtmlEntities;
const htmlentities = (new Entities()).encode;
const Resource = require('lib/models/Resource.js');
const htmlUtils = require('lib/htmlUtils.js');
const utils = require('../../utils');

function renderImageHtml(before, src, after, ruleOptions) {
	const r = utils.imageReplacement(src, ruleOptions.resources, ruleOptions.resourceBaseUrl);
	if (typeof r === 'string') return r;
	if (r) return '<img ' + before + ' ' + htmlUtils.attributesHtml(r) + ' ' + after + '/>';
	return '[Image: ' + htmlentities(resource.title) + ' (' + htmlentities(mime) + ')]';
}

function installRule(markdownIt, mdOptions, ruleOptions) {
	const htmlBlockDefaultRender = markdownIt.renderer.rules.html_block || function(tokens, idx, options, env, self) {
		return self.renderToken(tokens, idx, options);
	};

	const htmlInlineDefaultRender = markdownIt.renderer.rules.html_inline || function(tokens, idx, options, env, self) {
		return self.renderToken(tokens, idx, options);
	};

	const imageRegex = /<img(.*?)src=["'](.*?)["'](.*?)>/gi

	const handleImageTags = function(defaultRender) {
		return function(tokens, idx, options, env, self) {
			const token = tokens[idx];
			const content = token.content;

			if (!content.match(imageRegex)) return defaultRender(tokens, idx, options, env, self);

			return content.replace(imageRegex, (v, before, src, after) => {
				if (!Resource.isResourceUrl(src)) return defaultRender(tokens, idx, options, env, self);
				return renderImageHtml(before, src, after, ruleOptions);
			});
		}
	}

	// It seems images sometimes are inline, sometimes a block
	// to make sure they both render correctly.
	markdownIt.renderer.rules.html_block = handleImageTags(htmlBlockDefaultRender);
	markdownIt.renderer.rules.html_inline = handleImageTags(htmlInlineDefaultRender);
}

module.exports = function(context, ruleOptions) {
	return function(md, mdOptions) {
		installRule(md, mdOptions, ruleOptions);
	};
};