[OpenJDK 2D-Dev] [9] Review request for 8029339 Custom MultiResolution image support on HiDPI displays

[Jim Graham]

Hi Alexander,

Before we get too far down the road on this API, I think we understand 
the way in which MacOS processes multi-resolution images for HiDPI 
screens, but have we investigated the processes that Windows uses under 
Windows 8?  My impression is that Windows 8 has included a number of new 
techniques for dealing with the high resolution displays that it will 
run on in the Windows tablet and mobile industries and that these will 
also come into play as 4K displays (already available) become more 
common on the desktop.  We should make sure that what we come up with 
here can provide native compatibility with either platform's policies 
and standard practices.

If you've investigated the MS policies I'd like to see a summary so that 
we can consider them as we review this API...

			...jim

On 1/14/14 2:54 AM, Alexander Scherbatiy wrote:
>
> Hello,
>
> Could you review the fix:
>    bug: https://bugs.openjdk.java.net/browse/JDK-8029339
>    webrev: http://cr.openjdk.java.net/~alexsch/8029339/webrev.00
>
>    This is a proposal to introduce an API that allows to create a custom
> multi resolution image.
>
> I. It seems reasonable that the API should provide two basic operations:
>
>   1. Get the resolution variant based on the requested image width and
> height:
>      - Image getResolutionVariant(int width, int height)
>
>     Usually the system provides the scale factor which represents the
> number of pixels corresponding to each linear unit on the display.
>     However, it has sense to combine the scale factor and the current
> transformations to get the actual image size to be displayed.
>
>   2. Get all provided resolution variants:
>     - List<Image> getResolutionVariants()
>
>    There are several uses cases:
>     - Create a new multi-resolution image based on the given
> multi-resolution image.
>     - Pass to the native system the multi-resolution image. For example,
> a use can set to the system the custom multi-resolution cursor.
>
> II. There are some possible ways where the new API can be added
>
>   1. java.awt.Image.
>
>    The 2 new methods can be added to the Image class. A user can override
>    the getResolutionVariant() and getResolutionVariants() methods to
> provide the resolution variants
>    or there can be default implementations of these methods if a user
> puts resolution variants
>    to the list in the sorted order.
>
>    To check that the image has resolution variants the following
> statement can be used: image.getResolutionVariants().size() != 1
>
>    The disadvantage is that there is an overhead that the Image class
> should contain the List object and not all
>    images can have resolution variants.
>
>   2. Introduce new MultiResolutionImage interface.
>
>    A user should extend Image class and implement the
> MultiResolutionImage interface.
>
>    For example:
>    ---------------------
>      public class CustomMultiResolutionImage extends BufferedImage
>              implements MultiResolutionImage {
>
>          Image highResolutionImage;
>
>          public CustomMultiResolutionImage(BufferedImage baseImage,
>                  BufferedImage highResolutionImage) {
>              super(baseImage.getWidth(), baseImage.getHeight(),
> baseImage.getType());
>              this.highResolutionImage = highResolutionImage;
>              Graphics g = getGraphics();
>              g.drawImage(baseImage, 0, 0, null);
>              g.dispose();
>          }
>
>          @Override
>          public Image getResolutionVariant(int width, int height) {
>              return ((width <= getWidth() && height <= getHeight()))
>                      ? this : highResolutionImage;
>          }
>
>          @Override
>          public List<Image> getResolutionVariants() {
>              return Arrays.asList(this, highResolutionImage);
>          }
>      }
>    ---------------------
>
>   The current fix adds the MultiResolutionImage interface and public
> resolution variant rendering hints.
>
> Thanks,
> Alexandr.
>