Scalable Image

Scalable Image is a widget capable of drawing a scaled version of a bitmap. Simply change the width/height of the widget to resize the image. The quality of the scaled image depends of the rendering algorithm used. The rendering algorithm can be changed dynamically.

Note

This widget has a significant effect on the MCU load.

This widget does not support 1 bit per pixel color depth.

Scalable Image running in the simulator

Widget Group

The Scalable Image can be found in the Images widget group in TouchGFX Designer.

Scalable Image in TouchGFX Designer

Properties

The properties for a Scalable Image in TouchGFX Designer.

Property Group	Property Descriptions
Name	Name of the widget. Name is the unique identifier used in TouchGFX Designer and code.
Location	X and Y specify the top left corner of the widget relative to its parent. W and H specify the width and height of the widget. Lock specifies if the widget should be locked in its current X, Y, W and H. Locking the widget also disables interacting with the widget through the screen. Visible specifies the visibility of the widget. Making the widget invisible also disables interacting with the widget through the screen.
Image	Scaling Algorithm specifies the algorithm used for scaling the chosen image. Image specifies which image the widget should use.
Appearance	Alpha specifies the transparency of the widget. The alpha value ranges between 0 and 255 for the widget. 0 is fully transparent and 255 is solid.
Mixins	Draggable specifies if the widget is draggable at runtime. ClickListener specifies if the widget emits a callback when clicked. FadeAnimator specifies if the widget can animate changes to its Alpha value. MoveAnimator specifies if the widget can animate changes to X and Y values.

Interactions

The actions and triggers supported by a Scalable Image in TouchGFX Designer.

Actions

Widget specific action	Description
Resize widget	Resize the width and height of a widget.

Standard widget action	Description
Move widget	Move a widget to a new position over time.
Fade widget	Modify alpha value of widget over time.
Hide widget	Hides a widget (sets visibility to false).
Show widget	Make a hidden widget visible (sets visibility to true).

Triggers

A Scalable Image does not emit any triggers.

Performance

A Scalable Image heavily depends upon the MCU for scaling the image. Therefore, the Scalable Image is considered a demanding widget on most platforms.

For more details on drawing performance, read the read the General UI Component Performance section.

Examples

Generated Code

In the generated code for the View base class we can see how the Designer sets up a Scalable Image.

Screen1ViewBase.cpp

#include <gui_generated/screen1_screen/Screen1ViewBase.hpp>
#include "BitmapDatabase.hpp"

Screen1ViewBase::Screen1ViewBase()
{
    scalableImage.setBitmap(touchgfx::Bitmap(BITMAP_IMAGE_ID));
    scalableImage.setPosition(246, 36, 200, 200);
    scalableImage.setScalingAlgorithm(touchgfx::ScalableImage::NEAREST_NEIGHBOR);

    add(scalableImage);
}

void Screen1ViewBase::setupScreen()
{

}

Tip

You can use these functions and the others available in the ScalableImage class in user code. Remember to force a redraw by calling scalableImage.invalidate() if you change the appearance of the widget.

TouchGFX Designer Examples

To further explore the Scalable Image, try creating a new application within TouchGFX Designer with one of the following UI templates:

Scale and Zoom Example UI template in TouchGFX Designer

API Reference

Further reading

API reference for the ScalableImage class