Module image 

Images service, widget and other types.

Image

The Image! widget is the primary way of presenting images, the example below defines a repeating pattern image as the window background, the image source is embedded in this case, see ImageSource for other supported sources.

use zng::prelude::*;

Window! {
    widget::background = Image! {
        source = include_bytes!("../res/image/pattern.png");
        img_fit = zng::image::ImageFit::None;
        img_repeat = true;
    };
}

Mask

Mask images are loaded just like normal images, the mask::mask_image property can be set on any widget to apply a mask to it. The example below applies a mask to a button, by default the mask uses the alpha channel, see mask for more details.

use zng::{image::mask, prelude::*};

Button! {
    mask::mask_image = include_bytes!("../res/image/star.png");
}

Service

The IMAGES service manages image loading, the image cache and image rendering. Image decoding is implemented by the view-process, for this reason to get image with actual pixels the service must be used in a headed app or headless app with renderer, in a headless app without renderer all images are a placeholder dummy.

The images service also define security limits, the IMAGES.limits variable to configure these limits. See ImageLimits::default for the defaults.

use zng::{image, prelude::*};

image::IMAGES.limits().modify(|l| {
    l.allow_uri = image::UriFilter::allow_host("httpbin.org");
    l.max_encoded_len = 1.megabytes();
    l.max_decoded_len = 10.megabytes();
}); }

The example above changes the global limits to allow image downloads only from an specific host and only allow images with sizes less or equal to 1 megabyte and that only expands to up to 10 megabytes after decoding.

Full API

See zng_ext_image for the full image API and zng_wgt_image for the full widget API.

Modules

mask

Mask image properties.

Structs

IMAGES

Image loading, cache and render service.

IMAGE_RENDER

Controls properties of the render window used by IMAGES.render.

Image

W Image presenter.

ImageHash

A 256-bit hash for image entries.

ImageHasher

Hasher that computes a ImageHash.

ImageLimits

Limits for image loading and decoding.

ImageRenderArgs

Arguments for the ImageSource::Render closure.

Img

State of an ImageVar.

ImgErrorArgs

Arguments for on_error and img_error_fn.

ImgLoadArgs

Arguments for on_load.

ImgLoadingArgs

Arguments for img_loading_fn.

Enums

ImageCacheMode

Cache mode of IMAGES.

ImageDataFormat

Format of the image bytes.

ImageDownscale

Defines how an image is downscaled after decoding.

ImageFit

Image layout mode.

ImageRepeat

Image repeat mode.

ImageSource

The different sources of an image resource.

ImageSourceFilter

Represents a PathFilter and UriFilter.

Functions

img_align

P Sets the Align of all inner images within each image widget area.

img_cache

P Sets the cache mode of all inner images.

img_crop

P Sets a Rect that is a clip applied to all inner images before their layout.

img_downscale

P Custom pixel resize applied during image load/decode.

img_error_fn

P Sets the wgt_fn! that is used to create a content for the error message.

img_fit

P Sets the ImageFit of all inner images.

img_limits

P Sets custom image load and decode limits.

img_loading_fn

P Sets the wgt_fn! that is used to create a content for the loading message.

img_offset

P Sets a Point that is an offset applied to all inner images within each image widget area.

img_rendering

P Sets the ImageRendering of all inner images.

img_repeat

P Sets the ImageRepeat of all inner images.

img_repeat_spacing

P Sets the spacing between copies of the image if it is repeated.

img_scale

P Sets the scale applied to all inner images.

img_scale_density

P Sets if the image desired size is scaled considering the image and monitor pixel density.

img_scale_factor

P Sets if the image desired size is scaled by the screen scale factor.

is_error

P If the CONTEXT_IMAGE_VAR is an error.

is_loaded

P If the CONTEXT_IMAGE_VAR has successfully loaded.

on_error

P Image load or decode error event.

on_load

P Image loaded event.

render_retain

P If the render task is kept alive after a frame is produced, this is false by default meaning the image only renders once, if set to true the image will automatically update when the render widget requests a new frame.

Type Aliases

ImageVar

Represents an Img tracked by the IMAGES cache.

PathFilter

Represents a ImageSource::Read path request filter.

UriFilter

Represents a ImageSource::Download path request filter.