[back]Quick way to mask tree leaves

Contents

• The photo source
• Desaturate the image
• Contrast enhancement

The photo source ^

Trying to create a tree leaf sprite from a photo is often quite tricky and time consuming but use the following info below and it's possible to get good results relatively quickly.

The following (3 step) technique works best when a trees leaf mass is clearly defined so no other trees or objects get in the way of the main source needed for a sprite. In other words, when taking photographs try and compose the shot so the main mass of leaves/tree is backed by something 'flat', preferably the sky.

Design note : As with most photographs used for gaming it's best to try and take a source shot on a 'flat lit' day so the objects is as evenly lit as possible, without any strong highlights and darks or a stark difference between the two. Any 'flat' surface will do, it just needs to be relatively even in both tone and texture to make this process as straightforward as possible.

Source photograph taken against a flat 'overcast' sky.

Desaturate the image ^

Once the photograph is open in your photo editing application it's needs to be desaturated to a grey scale (black and white) image; removing colour from the photograph makes it easier to work with because you're then just dealing with a single set of tonal values rather than values associated with using a full RGB colour image.

Design note : trying to work with tonal colour can can make processing the image to get the mask harder and more time consuming as there is more going on when colour is involved.

You could at this point try and use this as a mask but it won't give you the clean silhouette that's needed for the actual mask, so the image needs another step.

Desaturating the image to convert it into a tonal grey scale (black and white) image.

Contrast enhancement ^

Editing this next step needs will depend on the photo editing application you use; the image is manipulated so the results are similar to a 'stencil' - a 'black/white' image. How this is done will vary but generally speaking altering the contrast and brightness of the image should be enough to at least create flat areas and hard shapes. The result is the actual image that will be used as a mask over the photograph.

Adding the mask over the photograph ^

Once you've got something approximate to the above 'mask' it then needs to be added as an mask layer to the original photograph. Again how this is done will vary dependant on the photo editing software being used but generally speaking you have two options; open the original photograph and then do one of the following;

• Load the image as a mask
  The results of the previous steps needs to be flattened and saved to a separate file - it should have no layers - and then 'loaded' into the images specifically as an alpha mask (this should automatically create an alpha channel)

• Copy/paste the image into an alpha channel
  Copy the mask image, then in the original photo image add a new alpha channel (there should be options to view and add/delete the channels contained in an image), select it and then simply 'paste' the copied mask into the newly create alpha channel.

This then means you have a clean mask in a few simple steps that will allow you to extract (copy/paste into a new document) and edit the leaf mass to create a much better tree sprite.

Mask image added to the original photo