Sharp

In the Open Event Webapp we came across an issue to scale the logo of the different generated events properly. On the outset, it looks a simple problem but it is a bit tricky when we consider the fact that different events have different logo sizes and we have to make sure that the logo is not too wide nor is it too long. Also, the aspect ratio of the image shouldn’t be changed otherwise it would look stretched and pixelated. Here are some screenshots to demonstrate the issue.

In the Facebook Developer Conference, the logo was too small

In the Open Tech Summit Event, the logo was too long and increased the height of the navigation bar

We decide some constraints regarding the width and the height of the logo. We don’t want the width of the logo to exceed greater than 110 pixels in order to not let it become too wide. It would look odd on small and medium screen if barely passable on bigger screens. We also don’t want the logo to become too long so we set a max-height of 45 pixels on the logo. So, we apply a class on the logo element with these properties

.logo-image {
 max-width: 110px;
 max-height: 45px;
}

But simply using these properties doesn’t work properly in some cases as shown in the above screenshots. An alternative approach is to resize the logo appropriately during the generation process itself. There are many different ways in which we can resize the logo. One of them was to scale the logo to a fixed dimension during the generation process. The disadvantage of that approach was that the event logo comes in different size and shapes. So resizing them to a fixed size will change its aspect ratio and it will appear stretched and pixelated. So, that approach is not feasible. We need to think of something different.  After a lot of thinking, we came up with an algorithm for the problem. We know the height of the logo would not be greater than 45px. We calculate the appropriate width and height of the logo, resize the image, and calculate dynamic padding which we add to the anchor element (inside which the image is located) if the height of the image comes out to be less than 45px. This is all done during the generation of the app. Note that the default padding is 5px and we add the extra pixels on top of it. This way, the logo doesn’t appear out of place or pixelated or extra wide and long. The detailed steps are mentioned below

• Declare variable padding = 5px
• Get the width, height and aspect ratio of the image.
• Set the height to 45px and calculate the width according to the aspect ratio. If the width <= 110px, then directly resize the image and no change in padding is necessary
• If the width > 110px, then make width constant to 110px and calculate height according to the aspect ratio. It will surely come less than 45px. Subtract the difference = (45 – height), divide it by 2 and add it to the padding variable.
• Apply padding variable on the anchor tag. Now every logo should be displayed nicely and we have fixed the height of the navigation bar = 55px for all cases.

Here is an excerpt of the code. The whole work and discussion can be viewed here

var optimizeLogo = function(image, socket, done) {
 sharp(image).metadata(function(err, metaData) {
   if(err) {
     return done(err);
   }
   var width = metaData.width;
   var height = metaData.height;
   var ratio = width/height;
   var padding = 5;
   var diffHeight = 0;

   height = 45;
   width = Math.floor(45 * ratio);
   if (width > 110) {
     width = 110;
     height = Math.floor(width/ratio);
     diffHeight = 45 - height;
     padding = padding + (diffHeight)/2;
   }
   sharp(image).resize(width, height).toFile(image + '.new', function(err, info) {
     return done(null, padding);
   });
 });
};

It solved the problem. Now the logos of all the events were displaying properly. They were neither too wide, long or short. Here are some screenshots to show the improvements.

Facebook Developer Conference

Open Tech Summit 2017

Resources:

• W3 Schools Web Tutorials Responsive Images
• David Walsh Blog Image Max-Width Property