Struct slint::Image

pub struct Image(_);

Expand description

An image type that can be displayed by the Image element. You can construct Image objects from a path to an image file on disk, using Self::load_from_path.

Another typical use-case is to render the image content with Rust code. For this it’s most efficient to create a new SharedPixelBuffer with the known dimensions and pass the mutable slice to your rendering function. Afterwards you can create an Image.

The following example creates a 320x200 RGB pixel buffer and calls an external low_level_render() function to draw a shape into it. Finally the result is stored in an Image with Self::from_rgb8():


fn low_level_render(width: u32, height: u32, buffer: &mut [u8]) {
    // render beautiful circle or other shapes here
}

let mut pixel_buffer = SharedPixelBuffer::<Rgb8Pixel>::new(320, 200);

low_level_render(pixel_buffer.width(), pixel_buffer.height(),
                 pixel_buffer.make_mut_bytes());

let image = Image::from_rgb8(pixel_buffer);

Another use-case is to import existing image data into Slint, by creating a new Image through cloning of another image type.

The following example uses the popular image crate to load a .png file from disk, apply brightening filter on it and then import it into an Image:

let mut cat_image = image::open("cat.png").expect("Error loading cat image").into_rgba8();

image::imageops::colorops::brighten_in_place(&mut cat_image, 20);

let buffer = SharedPixelBuffer::<Rgba8Pixel>::clone_from_slice(
    cat_image.as_raw(),
    cat_image.width(),
    cat_image.height(),
);
let image = Image::from_rgba8(buffer);

A popular software (CPU) rendering library in Rust is tiny-skia. The following example shows how to use tiny-skia to render into a SharedPixelBuffer:

let mut pixel_buffer = SharedPixelBuffer::<Rgba8Pixel>::new(640, 480);
let width = pixel_buffer.width();
let height = pixel_buffer.height();
let mut pixmap = tiny_skia::PixmapMut::from_bytes(
    pixel_buffer.make_mut_bytes(), width, height
).unwrap();
pixmap.fill(tiny_skia::Color::TRANSPARENT);

let circle = tiny_skia::PathBuilder::from_circle(320., 240., 150.).unwrap();

let mut paint = tiny_skia::Paint::default();
paint.shader = tiny_skia::LinearGradient::new(
    tiny_skia::Point::from_xy(100.0, 100.0),
    tiny_skia::Point::from_xy(400.0, 400.0),
    vec![
        tiny_skia::GradientStop::new(0.0, tiny_skia::Color::from_rgba8(50, 127, 150, 200)),
        tiny_skia::GradientStop::new(1.0, tiny_skia::Color::from_rgba8(220, 140, 75, 180)),
    ],
    tiny_skia::SpreadMode::Pad,
    tiny_skia::Transform::identity(),
).unwrap();

pixmap.fill_path(&circle, &paint, tiny_skia::FillRule::Winding, Default::default(), None);

let image = Image::from_rgba8_premultiplied(pixel_buffer);

Sending Image to a thread

Image is not Send, because it uses internal cache that are local to the Slint thread. If you want to create image data in a thread and send that to slint, construct the SharedPixelBuffer in a thread, and send that to Slint’s UI thread.

std::thread::spawn(move || {
    let mut pixel_buffer = SharedPixelBuffer::<Rgba8Pixel>::new(640, 480);
    // ... fill the pixel_buffer with data as shown in the previous example ...
    slint::invoke_from_event_loop(move || {
        // this will run in the Slint's UI thread
        let image = Image::from_rgba8_premultiplied(pixel_buffer);
        // ... use the image, eg:
        // my_ui_handle.upgrade().unwrap().set_image(image);
    });
});

Implementations§

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impl Image

pub fn load_from_path(path: &Path) -> Result<Image, LoadImageError>

Load an Image from a path to a file containing an image

pub fn from_rgb8(buffer: SharedPixelBuffer<RGB<u8>>) -> Image

Creates a new Image from the specified shared pixel buffer, where each pixel has three color channels (red, green and blue) encoded as u8.

pub fn from_rgba8(buffer: SharedPixelBuffer<RGBA<u8, u8>>) -> Image

Creates a new Image from the specified shared pixel buffer, where each pixel has four color channels (red, green, blue and alpha) encoded as u8.

pub fn from_rgba8_premultiplied( buffer: SharedPixelBuffer<RGBA<u8, u8>> ) -> Image

Creates a new Image from the specified shared pixel buffer, where each pixel has four color channels (red, green, blue and alpha) encoded as u8 and, in contrast to Self::from_rgba8, the alpha channel is also assumed to be multiplied to the red, green and blue channels.

Only construct an Image with this function if you know that your pixels are encoded this way.

pub fn size(&self) -> Size2D<u32, UnknownUnit>

Returns the size of the Image in pixels.

pub fn path(&self) -> Option<&Path>

Returns the path of the image on disk, if it was constructed via Self::load_from_path.

For example:

let path_buf = Path::new(env!("CARGO_MANIFEST_DIR"))
    .join("../../examples/printerdemo/ui/images/cat.jpg");
let image = Image::load_from_path(&path_buf).unwrap();
assert_eq!(image.path(), Some(path_buf.as_path()));