Drawing Pad

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Sunday, June 20, 2021PrintSubscribe
Drawing Pad

Taking photos in business apps often requires the visual annotation of the image. Another common scenario is sketching on the pre-defined template. Touch UI provides a built-in drawing pad that works seamlessly with the BLOB fields of your app. The feature is enabled by default and can be activated with a tap on the “Draw” button.

The drawing pad will be immediately displayed in fullscreen mode in response to the tap. It offers several tools: pen, highlighter, blur, and eraser with multiple levels of undo and redo. You can draw with a finger or a stylus compatible with the touch-screen device. Mouse pointers will also work. 

The “pen” and “highlighter” will impact the image as one would expect. The “blur” tool will blur the image contents. The “eraser” will remove the effect of the other tools.

Developers can handle the blobdrawtoolbox.app event triggered on the document and override the available tools and their properties such as the width of the stroke and the color choices. The toolbox property of the event provides access to the default tool configuration.

The drawing is composed of multiple layers. Saving of the drawing will compose the final image that will be submitted to the server when the data record is saved. The end user can perform multiple sessions of drawing prior to the submission since the layers remain preserved until the record has been saved.

Sketching on the template will require a default image to be provided. Create a custom script to handle the getdefaultblob.app event. The field property will indicate the name of the blob field that does not have a value. If e.blob.url or e.blob.icon properties are assigned in the event handler, then the corresponding image will be downloaded or a material icon will be drawn.

For example, the following handler will cause the framework to create a blue material icon for the category picture in the application.

The default image based on an icon may serve as a blob stub whenever the optional image is required. The end user may tap on the image and have it replaced with their by either taking a photo on the device or choosing a previously created image.

Tapping on the default blob image will always activate the drawing pad if the BLOB data field is tagged as image-user-defined-none. The end user will not be able to replace the template image.

The end users may take real-world photos and provide the visual comments with the drawing pad tools. Keep in mind that the huge photographs taken by modern day cameras will likely be redundant for business purposes. Make sure to specify the image-size-WxH tag to engage the image preprocessor to enforce the pre-defined image photo size and graphical annotations. 

Drawing pad provides a powerful tool for the line-of-business apps. Naturally it may not always be desirable to allow image alteration. Tag the blob data field as image-editor-none to disable the drawing pad.

By default the blob images are rendered as thumbnails. Tag the data fields as image-original-always if the original image must be displayed both when the users are viewing and editing the data. The field with the tag image-original-editing will show the original image if the blob is presented in the “edit” mode. End users may still download the original image when viewing the record.

The drawing pad will work on the small devices, tablets, and huge desktop monitors.