Tham Si Mun - Project Portfolio

The filter mechanism is facilitated by scrimage, an external API Library that provides image filters methods for our image editor. The gradle script declares a compile-time dependency on this external API through the coordinates: group: 'com.sksamuel.scrimage', name: 'scrimage-filters_2.12', version: '3.0.0-alpha4'.

The image filters feature is facilitated by CurrentEdit. It uses the following operations:

The filter feature mainly consists of:

The following describes the main operations and processes for each command stated above.

This command calls for an adjustment of contrast on an opened image. After adjusting the contrast, it adds this specific command called by the user to the List<Commands> belonging to the tempImage found in CurrentEdit which saves the editing history of the opened image.

Given below is an example usage scenario of how contrast behaves at each step as shown in Sequence Diagram for Contrast Command. [This applies to the other image filter commands as well.]

Step 1. When the user runs an open command to edit an image, it invokes a method which creates an instance of an Image that stores the file path of the image, its history of edits [List<Command>] and its metadata. This Image object is saved under the variable name tempImage in CurrentEdit for editing.

Step 2. When the user enters the command (e.g. contrast 0.3), the entered command is parsed and the command will be executed.

Step 3. During execution, the execute method in the ContrastCommand class first invokes CurrentEdit#tempImageDoNotExist to check if an image is opened. If no image is opened, it will throw an error message to inform the user to open an image for editing first. Else, the execute method will invoke CurrentEdit#getTempImage() to get the tempImage from CurrentEdit.

Step 4. Upon retrieving the tempImage, the execute method creates a ContrastFilter instance provided by the external library [scrimage] which takes in a double contrast ratio value. This ContrastFilter will then be applied to the image retrieved from the file path of tempImage.

Step 5. After applying the ContrastFilter on the opened image, CurrentEdit#updateTempImage() is invoked to save the newly edited image and replace the previous one in the file path of the tempImage.

Step 6. The execute method then checks if the boolean isNewCommand is true. If it is true, it indicates that the command is a new contrast command called directly from the user and not through an undo/redo command. This triggers Step 7 in the line below. Otherwise, the command’s execution ends in this step.

Step 7. isNewCommand is set to false to signal that this command is not a new contrast command if it is executed again through the undo/redo command.

Step 8. CurrentEdit#addCommand(this) is invoked to add this command to the List<Command> in tempImage for the undo/redo function and CurrentEdit#displayTempImage() is used to display the edited image on the graphical user interface.

This command calls for an adjustment of brightness on an opened image. After adjusting the brightness, it adds this specific command called by the user to the List<Commands> belonging to the tempImage found in currentEdit which saves the editing history of the opened image.

Refer to the example usage scenario, sequence diagram and design considerations in Contrast Command.

This command calls for a transformation of an opened image to a black and white image. After applying the black and white filter, it adds this specific command called by the user to the List<Commands> belonging to the tempImage found in currentEdit which saves the editing history of the opened image.

Refer to the example usage scenario, sequence diagram and design considerations in Contrast Command.

The setpreset function is facilitated by CurrentEdit and TransformationSet. It uses the following operations:

The following sequence diagram shows how setpreset works:

Given below is an example usage scenario of how setpreset behaves at each step as shown in Sequence Diagram for Set Preset Command.

Step 1. When the user enters the command (e.g. setpreset preset1), the entered command is parsed and the command will be executed.

Step 2. During execution, the execute method in the SetPresetCommand class first invokes CurrentEdit#tempImageDoNotExist to check if an image is opened. If no image is opened, an error message will be displayed to remind the user to open an image for editing first.

Step 3. If an image is opened, the execute method will invoke CurrentEdit#getTempImage() to retrieve the tempImage from CurrentEdit.

Step 4. TransformationSet#isPresent(String) is then invoked to check if there is a preset of commands saved under the name specified by the user. If the method returns false, an error message will be displayed to inform the user that there is no preset of commands saved under the name he/she specified.

Step 5. Else, the method TransformationSet#findTransformation(String) is called to retrieve the List<Command> saved under the specified preset name. TransformationSet#hasWaterMarkCommand(String) is also invoked to check if the List<Command> has a WaterMarkCommand.

Step 6. Commands in the List<Command> will be executed one by one to apply the respective edits to the opened image. If any of the commands throws an exception (e.g. If a watermark is already applied on an image, the execution of a preset of commands which contains a WaterMarkCommand on the same image will throw an error message to indicate that there is already a watermark.), the method CurrentEdit#replaceTempWithOriginal will undo all the changes made to the image.

Step 6. Lastly, CurrentEdit#addCommand(this) is invoked to add this command to the List<Command> in tempImage for the undo/redo function and CurrentEdit#displayTempImage() is used to display the edited image on the graphical user interface.

In the end, the first alternative is chosen as we want users to see the immediate effect of the commands so that they can make changes or undo the edits if they do not like what they see.