Loading thumbnails on a canvas takes too long, with swt

Question

Hi I have an application that loads all the images of a folder in a canvas, vertically. Like thumbnails. These folders have usually more than 20 images, around 1mb sometimes even 2. I created a class called Index, that extend canvas.

I managed to load all the images and resize them to the proper size (the original size is around 1280x1985, yeah they are quit big. But it takes too long, and I think I know why but I dont know how fix it or do it better.

public void loadImages(){
        System.out.println("Loading Images");
        List<String> imageList = new ArrayList<String>();
        imageList = listDirImages(this.strDir);
        int listSize=imageList.size();
        for(int i=0;i<listSize;i++){
            System.out.println(imageList.get(i));
            Image sourceImage;
            System.out.println(strDir.concat("/".concat(imageList.get(i))));
            try {
                sourceImage = new Image(getDisplay(),strDir.concat("/".concat(imageList.get(i))));
                //sourceImage[i] = new Image(getDisplay(),strDir.concat("/".concat(lsImagenes.get(i))));
            }catch(Exception e){
                System.out.println(e);
                //band=1;
            }
        }
    }

This function uses the directory, then it calls to a function to list all the images. It lists all the images. The original code was different but i tried to eliminate the code to see where it is taking so long. Original sourceImage was an array of images (I dont know if that is better), and I resized the images creating new ones, but it took longer to create them.

with 25 images it takes almost 45 seconds to load this part, I know the problem is that i am loading the full image, and they are quite heavy. Is there a way to load them directly to a thumbnail? Some folders have around 80 pages, that is like 2 minutes. (For one part I think i have to this as thread, so the whole program could run other things while it is loading the index.

Answer 1

You need thumbnails to be pre-build on the server and just load them with the javascript. Even if there is a way to load images directly in thumbnails the client will still download the full size image to create the thumbnail and this is not good for the network bandwidth.