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Diffstat (limited to 'core/src/image.rs')
| -rw-r--r-- | core/src/image.rs | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/core/src/image.rs b/core/src/image.rs new file mode 100644 index 00000000..97a9eb2c --- /dev/null +++ b/core/src/image.rs @@ -0,0 +1,119 @@ +//! Control the fit of some content (like an image) within a space + +use crate::Size; + +/// How the image should scale to fit the bounding box of the widget +/// +/// Each variant of this enum is a strategy that can be applied for resolving +/// differences in aspect ratio and size between the image being displayed and +/// the space its being displayed in. +/// +/// For an interactive demonstration of these properties as they are implemented +/// in CSS, see [Mozilla's docs][1], or run the `tour` example +/// +/// [1]: https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit +#[derive(Debug, Hash, Clone, Copy, PartialEq, Eq)] +pub enum ContentFit { + /// Scale as big as it can be without needing to crop or hide parts + /// + /// The image will be scaled (preserving aspect ratio) so that it just fits + /// within the window. This won't distort the image or crop/hide any edges, + /// but if the image doesn't fit perfectly, there may be whitespace on the + /// top/bottom or left/right. + /// + /// This is a great fit for when you need to display an image without losing + /// any part of it, particularly when the image itself is the focus of the + /// screen. + Contain, + + /// Scale the image to cover all of the bounding box, cropping if needed + /// + /// This doesn't distort the image, and it ensures that the widget's area is + /// completely covered, but it might crop off a bit of the edges of the + /// widget, particularly when there is a big difference between the aspect + /// ratio of the widget and the aspect ratio of the image. + /// + /// This is best for when you're using an image as a background, or to fill + /// space, and any details of the image around the edge aren't too + /// important. + Cover, + + /// Distort the image so the widget is 100% covered without cropping + /// + /// This stretches the image to fit the widget, without any whitespace or + /// cropping. However, because of the stretch, the image may look distorted + /// or elongated, particularly when there's a mismatch of aspect ratios. + Fill, + + /// Don't resize or scale the image at all + /// + /// This will not apply any transformations to the provided image, but also + /// means that unless you do the math yourself, the widget's area will not + /// be completely covered, or the image might be cropped. + /// + /// This is best for when you've sized the image yourself. + None, + + /// Scale the image down if it's too big for the space, but never scale it up + /// + /// This works much like [`Contain`](Self::Contain), except that if the + /// image would have been scaled up, it keeps its original resolution to + /// avoid the bluring that accompanies upscaling images. + ScaleDown, +} + +impl ContentFit { + /// Attempt to apply the given fit for a content size within some bounds + /// + /// The returned value is the recommended scaled size of the content. + pub fn fit(&self, content: Size, bounds: Size) -> Size { + let content_ar = content.width / content.height; + let bounds_ar = bounds.width / bounds.height; + + match self { + Self::Contain => { + if bounds_ar > content_ar { + Size { + width: content.width * bounds.height / content.height, + ..bounds + } + } else { + Size { + height: content.height * bounds.width / content.width, + ..bounds + } + } + } + Self::Cover => { + if bounds_ar < content_ar { + Size { + width: content.width * bounds.height / content.height, + ..bounds + } + } else { + Size { + height: content.height * bounds.width / content.width, + ..bounds + } + } + } + Self::Fill => bounds, + Self::None => content, + Self::ScaleDown => { + if bounds_ar > content_ar && bounds.height < content.height { + Size { + width: content.width * bounds.height / content.height, + ..bounds + } + } else if bounds.width < content.width { + Size { + height: content.height * bounds.width / content.width, + ..bounds + } + } else { + content + } + } + } + } +} |