#6504: Optimize channel banner

ui/component/channelThumbnail/view.jsx

@@ -5,12 +5,7 @@ import classnames from 'classnames';
 import Gerbil from './gerbil.png';
 import FreezeframeWrapper from 'component/fileThumbnail/FreezeframeWrapper';
 import ChannelStakedIndicator from 'component/channelStakedIndicator';
-import { getThumbnailCdnUrl } from 'util/thumbnail';
-
-const FONT_PX = 16.0;
-const IMG_XSMALL_REM = 2.1;
-const IMG_SMALL_REM = 3.0;
-const IMG_NORMAL_REM = 10.0;
+import OptimizedImage from 'component/optimizedImage';
 
 type Props = {
   thumbnail: ?string,
@@ -53,8 +48,6 @@ function ChannelThumbnail(props: Props) {
   const channelThumbnail = thumbnail || thumbnailPreview;
   const isGif = channelThumbnail && channelThumbnail.endsWith('gif');
   const showThumb = (!obscure && !!thumbnail) || thumbnailPreview;
-  const thumbnailRef = React.useRef(null);
-  const thumbnailSize = calcRenderedImgWidth(); // currently always 1:1
 
   // Generate a random color class based on the first letter of the channel name
   const { channelName } = parseURI(uri);
@@ -67,20 +60,6 @@ function ChannelThumbnail(props: Props) {
     colorClassName = `channel-thumbnail__default--4`;
   }
 
-  function calcRenderedImgWidth() {
-    let rem;
-    if (xsmall) {
-      rem = IMG_XSMALL_REM;
-    } else if (small) {
-      rem = IMG_SMALL_REM;
-    } else {
-      rem = IMG_NORMAL_REM;
-    }
-
-    const devicePixelRatio = window.devicePixelRatio || 1.0;
-    return Math.ceil(rem * devicePixelRatio * FONT_PX);
-  }
-
   React.useEffect(() => {
     if (shouldResolve && uri) {
       doResolveUri(uri);
@@ -94,15 +73,6 @@ function ChannelThumbnail(props: Props) {
       </FreezeframeWrapper>
     );
   }
-
-  let url = channelThumbnail;
-  // @if TARGET='web'
-  // Pass image urls through a compression proxy, except for GIFs.
-  if (thumbnail && !(isGif && allowGifs)) {
-    url = getThumbnailCdnUrl({ thumbnail, width: thumbnailSize, height: thumbnailSize, quality: 85 });
-  }
-  // @endif
-
   return (
     <div
       className={classnames('channel-thumbnail', className, {
@@ -113,13 +83,10 @@ function ChannelThumbnail(props: Props) {
       })}
     >
       {!showThumb && (
-        <img
-          ref={thumbnailRef}
+        <OptimizedImage
           alt={__('Channel profile picture')}
           className="channel-thumbnail__default"
-          src={!thumbError && url ? url : Gerbil}
-          width={thumbnailSize}
-          height={thumbnailSize}
+          src={!thumbError && channelThumbnail ? channelThumbnail : Gerbil}
           loading={noLazyLoad ? undefined : 'lazy'}
           onError={() => setThumbError(true)} // if thumb fails (including due to https replace, show gerbil.
         />
@@ -129,13 +96,10 @@ function ChannelThumbnail(props: Props) {
           {showDelayedMessage && thumbError ? (
             <div className="chanel-thumbnail--waiting">{__('This will be visible in a few minutes.')}</div>
           ) : (
-            <img
-              ref={thumbnailRef}
+            <OptimizedImage
               alt={__('Channel profile picture')}
               className="channel-thumbnail__custom"
-              src={!thumbError && url ? url : Gerbil}
-              width={thumbnailSize}
-              height={thumbnailSize}
+              src={!thumbError && channelThumbnail ? channelThumbnail : Gerbil}
               loading={noLazyLoad ? undefined : 'lazy'}
               onError={() => setThumbError(true)} // if thumb fails (including due to https replace, show gerbil.
             />

ui/component/optimizedImage/index.js

@@ -0,0 +1,2 @@
+import OptimizedImage from './view';
+export default OptimizedImage;

ui/component/optimizedImage/view.jsx

@@ -0,0 +1,108 @@
+// @flow
+import React from 'react';
+import { getThumbnailCdnUrl } from 'util/thumbnail';
+
+function scaleToDevicePixelRatio(value: number, window: any) {
+  const devicePixelRatio = window.devicePixelRatio || 1.0;
+  return Math.ceil(value * devicePixelRatio);
+}
+
+type Props = {
+  src: string,
+  objectFit?: string,
+};
+
+function OptimizedImage(props: Props) {
+  const { objectFit, src, ...imgProps } = props;
+  const [optimizedSrc, setOptimizedSrc] = React.useState('');
+  const ref = React.useRef<any>();
+
+  function getOptimizedImgUrl(url, width, height) {
+    let optimizedUrl = url;
+    if (url && !url.startsWith('/public/')) {
+      optimizedUrl = url.trim().replace(/^http:\/\//i, 'https://');
+
+      // @if TARGET='web'
+      if (!optimizedUrl.endsWith('.gif')) {
+        optimizedUrl = getThumbnailCdnUrl({ thumbnail: optimizedUrl, width, height, quality: 85 });
+      }
+      // @endif
+    }
+    return optimizedUrl;
+  }
+
+  function getOptimumSize(elem) {
+    if (!elem || !elem.parentElement || !elem.parentElement.clientWidth || !elem.parentElement.clientHeight) {
+      return null;
+    }
+
+    let width = elem.parentElement.clientWidth;
+    let height = elem.parentElement.clientHeight;
+
+    width = scaleToDevicePixelRatio(width, window);
+    height = scaleToDevicePixelRatio(height, window);
+
+    // Round to next 100px for better caching
+    width = Math.ceil(width / 100) * 100;
+    height = Math.ceil(height / 100) * 100;
+
+    // Reminder: CDN expects integers.
+    return { width, height };
+  }
+
+  function adjustOptimizationIfNeeded(elem, objectFit, origSrc) {
+    if (objectFit === 'cover' && elem) {
+      const containerSize = getOptimumSize(elem);
+      if (containerSize) {
+        // $FlowFixMe
+        if (elem.naturalWidth < containerSize.width) {
+          // For 'cover', we don't want to stretch the image. We started off by
+          // filling up the container height, but the width still has a gap for
+          // this instance (usually due to aspect ratio mismatch).
+          // If the original image is much larger, we can request for a larger
+          // image so that "objectFit=cover" will center it without stretching and
+          // making it blur. The double fetch might seem wasteful, but on
+          // average the total transferred bytes is still less than the original.
+          const probablyMaxedOut = elem.naturalHeight < containerSize.height;
+          if (!probablyMaxedOut) {
+            const newOptimizedSrc = getOptimizedImgUrl(origSrc, containerSize.width, 0);
+            if (newOptimizedSrc && newOptimizedSrc !== optimizedSrc) {
+              setOptimizedSrc(newOptimizedSrc);
+            }
+          }
+        }
+      }
+    }
+  }
+
+  React.useEffect(() => {
+    const containerSize = getOptimumSize(ref.current);
+    if (containerSize) {
+      const width = 0; // The CDN will fill the zeroed attribute per image's aspect ratio.
+      const height = containerSize.height;
+
+      const newOptimizedSrc = getOptimizedImgUrl(src, width, height);
+
+      if (newOptimizedSrc !== optimizedSrc) {
+        setOptimizedSrc(newOptimizedSrc);
+      }
+    } else {
+      setOptimizedSrc(src);
+    }
+  }, []); // eslint-disable-line react-hooks/exhaustive-deps
+
+  if (!src) {
+    return null;
+  }
+
+  return (
+    <img
+      ref={ref}
+      {...imgProps}
+      src={optimizedSrc}
+      onLoad={() => adjustOptimizationIfNeeded(ref.current, objectFit, src)}
+    />
+  );
+}
+
+export default OptimizedImage;

ui/page/channel/view.jsx

@@ -21,6 +21,7 @@ import HelpLink from 'component/common/help-link';
 import ClaimSupportButton from 'component/claimSupportButton';
 import ChannelStakedIndicator from 'component/channelStakedIndicator';
 import ClaimMenuList from 'component/claimMenuList';
+import OptimizedImage from 'component/optimizedImage';
 import Yrbl from 'component/yrbl';
 import I18nMessage from 'component/i18nMessage';
 // $FlowFixMe cannot resolve ...
@@ -220,7 +221,7 @@ function ChannelPage(props: Props) {
           <ClaimMenuList uri={claim.permanent_url} channelUri={claim.permanent_url} inline isChannelPage />
         </div>
         {cover && <img className={classnames('channel-cover__custom')} src={PlaceholderTx} />}
-        {cover && <img className={classnames('channel-cover__custom')} src={cover} />}
+        {cover && <OptimizedImage className={classnames('channel-cover__custom')} src={cover} objectFit="cover" />}
         <div className="channel__primary-info">
           <ChannelThumbnail className="channel__thumbnail--channel-page" uri={uri} allowGifs hideStakedIndicator />
           <h1 className="channel__title">