Transparency and Green Screen

Chiizu Event Picture Retailer has a very powerful transparency engine.

Green Screen (or any other color) transparency can be used to create fantasy photos such as the one displayed below:

The photos of the subjects were taken in front of a "green screen".  The green pixels were then removed to create transparency so the images could be placed into the final photo.

This example also included a foreground overlay (the Luna Park entrance) and a background - the sky.

There are three ways to make images transparent:

Any of these approaches can be combined to eliminate the background for fantasy photos, etc.

Colors

Selecting one or more colors can be a very effective way to create transparency.

For example:

Select the photo:

Enable the Select colors:

Pick a color from the photo with the dropper:

The result looks like this:

There is still some green in the lower corner.  We can either change the brightness threshold to eliminate the green (this increases the color range of pixels made transparent) or add another color sample.

Let's add another color by using the Pick Color tool again:

There is still some green in the lower right area.

So let's tune it out by increasing the Brightness threshold of the second color sample.

And now it's eliminated and we have a good result.

You can now save these settings if they are working well in your environment.

Pixels that are close to the color selected will also be made transparent.  Pixels that are further away, but still within a reasonable amount are made semi transparent.  This provides a soft edge between the foreground and background.

The brightness slider adds or removes pixels that are brighter or darker then the selected color but with approximately the same relative RGB values.

The 100% transparency and Variable transparency allow for fine tuning to ensure the best result is achieved.

Shadow Highlight

Shadow highlight is very similar to using colors above.  The main difference is that instead of having any number of colors to create transparency, you select a highlight of the background and a shadow area, then all colors in between these will become transparent.

Since lighting of a photograph will nearly always vary at least slightly, this method allows you to remove a greater range of colors than if you had to pick each one individually. Click the "Pick Highlight Color" button and select a color from the source image by clicking it with the mouse - here you should select the brightest color of the range you wish to remove. Now click the "Pick Shadow Color" button, and repeat the process, this time selecting the darkest color of the range you wish to remove.

This is good for unevenly lit backgrounds (ie: with a gradation).  Backgrounds with obvious shadows might be better treated with the color picking method above - one for the lit area and one for the shadow.

Background Subtraction

Background subtraction is an interesting method that uses a photo with no subjects in it (ie: the background) to compare with the photo with the subjects. The areas where the photos are the same (or very similar) are made transparent.

 
This can help with very challenging environments with complex backgrounds.

For example this photo has many imperfections in the background including a wooden stage, gaps, shadows, creased paper, etc.

Here is the background image

and here with the subjects included

A combination of Background Subtraction and Shadow Highlight approaches gave a reasonable result for this setup.  The studio was further  optimized to improve the result as it was not an optimal environment for transparency treatment.

Either a fixed background file or a folder can be selected.   If a folder is selected, the most recent image will be used as the background image.

Transparency / Opacity Painter

This is a useful tool for fixing up problem transparency situations.  Simply select a brush to either:

There is an undo button to remove the last change made and a clear button to remove all painting.