Dynamic Animation Library
This tutorial describes the use of Resources in Dali, currently Image resources.
Resources in Dali can apply Images or 3D Models.
The common method to access these resources is through Visuals.
Controls then use these visuals to display what is required.
Images are defined by an url which can be local or remote (internet).
The following formats are supported
| Supported image formats | extentsion |
|---|---|
| Bitmap | .bmp |
| Gif | .gif |
| Jpeg | .jpeg |
| Khronos Texture | .ktx |
| PNG | .png |
| Mircosoft Icons | .ico |
| WAP Bitmap | .wbmp |
Controls should process the provoded url and internally create the matching Image visual.
Visual creation will automatically determine if the Image is an N_PATCH, SVG, GIF not regular image from the image data.
| Property Name | Description |
|---|---|
| ALPHA_MASK_URL | url to an image that will mask the main content image |
| CROP_TO_MASK | Flag to determine if main content image should crop to match mask size |
| FITTING_MODE | By default the image will shrink to fit the desiredHeight and desiredWidth, other modes available |
| SAMPLING_MODE | The type of sampling to be used. Default is Box. |
| DESIRED_WIDTH | The width you would like the Image to be. Affected by FITTING_MODE |
| DESIRED_HEIGTH | The height you would like the Image to be. Affected by FITTING_MOD |
| SYNCHRONOUS_LOADING | If loading should block the execution thread, disabled by Default. |
| PIXEL_AREA | Can be set to display only a portion of the Image |
| WRAP_MODE_U | Define how sampling should behave for u coordinate |
| WRAP_MODE_V | Define how sampling should behave for v coordinate |
| ATLASING | Whether to use the texture atlas to speed up loading times, enabled by default |
| Property Name | Description |
|---|---|
| BORDER | Specifies border values for N-Patch images |
| BORDER_ONLY | Specifies if ONLY borders to be shown for N-Patch images |
| Property Name | Description |
|---|---|
| BATCH_SIZE | Number of Images to decode before animation starts, Default is 1. |
| CACHE_SIZE | Number of images to keep cached, Can increase or decrease depending on memory avaiable. |
| FRAME_DELAY | Millisecond delay between frames |
Synchronous loading has niche uses, eg. ensuring image has loaded before continuing to execute application code,
the common use is to connect to the control’s ResourceReady Signal and peform operations at that point.
Images are automatically cached, if the ATLASING is not disable then may be in an Atlas too.
If an Image (ImageVisual) is added then removed then added to the stage loading times can be reduced by keeping the
visual registered with the control.
This is useful for Control writers and exaplained further in “Creating Controls with Visuals” tutorial.
An application loading images may want to display them at lower resolution than their native resolution.
To support this, DALi can resize an image at load time so that its in-memory copy uses less space and its visual quality
benefits from being prefiltered.
DESIRED_WIDTH and DESIRED_HEIGHT can be set to the Image visual and then FITTING_MODE.
The Dali::FittingMode namespace provides 4 algorithms, which can be used to fit an image to a desired rectangle,
a desired width, or a desired height.
The fitting modes and suggested use cases are as follows:
| Fitting mode | Suggested use case |
|---|---|
| FittingMode::SHRINK_TO_FIT | Fit full image inside desired width & height, potentially not filling one of either the desired image width or height with pixels. |
| FittingMode::SCALE_TO_FILL | The image is centred in the desired dimensions, exactly touchingin one dimension, with image regions outside the other desired dimension cropped. |
| FittingMode::FIT_WIDTH | Image fills whole width. Height is scaled proportionately to maintain aspect ratio. |
| FittingMode::FIT_HEIGHT | Image fills whole height. Width is scaled proportionately to maintain aspect ratio. |