getView()

public View getView(int position, View convertView, ViewGroup parent) {
        ImageView iv;
        final Document document = getItem(position);
        final int currentColumnCount = Utils.getInteger(R.integer.grid_column_count);

        if (convertView == null) {
            iv = new ImageView(App.getContext());
            iv.setAdjustViewBounds(true);
        } else {
            iv = (ImageView)convertView;
        }

        float margin = Utils.dp2px(Utils.getDimension(R.dimen.common_padding_small))*(currentColumnCount-1);
        int ivWidth = (int) ((Utils.getDisplayXY()[0]-margin) / currentColumnCount);
        float thumbRatio = (float) document.getHeight() / (float)document.getWidth();

        int ivHeight = (int)( ivWidth * thumbRatio);

        if (ivHeight >= parent.getHeight() ){ //TODO remove after GridView lib new release
            ivHeight = parent.getHeight() - (int)Utils.getDimension(R.dimen.common_padding_large);
        }

        iv.setLayoutParams(new ViewGroup.LayoutParams(ivWidth,ivHeight));
        ImageLoader.getInstance().displayImage(document.getPath_thumbnail(), iv);

        return iv;
    }