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Zoom images to where the cursor points

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Signed-off-by: Robin Townsend <robin@robin.town>
This commit is contained in:
Robin Townsend 2021-07-21 02:13:30 -04:00
parent 91cf27e252
commit 3911666c52
1 changed files with 60 additions and 23 deletions
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79
src/components/views/elements/ImageView.tsx
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@ -160,41 +160,82 @@ export default class ImageView extends React.Component<IProps, IState> {
});
};
private zoom(delta: number) {
const newZoom = this.state.zoom + delta;
private zoomDelta(delta: number, zoomX?: number, zoomY?: number) {
this.zoom(this.state.zoom + delta, zoomX, zoomY);
}
private zoom(zoomLevel: number, zoomX?: number, zoomY?: number) {
const oldZoom = this.state.zoom;
const newZoom = Math.min(zoomLevel, this.state.maxZoom);
if (newZoom <= this.state.minZoom) {
// Zoom out fully
this.setState({
zoom: this.state.minZoom,
translationX: 0,
translationY: 0,
});
return;
}
if (newZoom >= this.state.maxZoom) {
this.setState({ zoom: this.state.maxZoom });
return;
}
} else if (zoomX === undefined && zoomY === undefined) {
// Zoom relative to the center of the view
this.setState({
zoom: newZoom,
translationX: this.state.translationX * newZoom / oldZoom,
translationY: this.state.translationY * newZoom / oldZoom,
});
} else {
// Zoom relative to the given point on the image.
// First we need to figure out the offset of the anchor point
// relative to the center of the image, accounting for rotation.
let offsetX;
let offsetY;
switch (((this.state.rotation % 360) + 360) % 360) {
case 0:
offsetX = this.image.current.clientWidth / 2 - zoomX;
offsetY = this.image.current.clientHeight / 2 - zoomY;
break;
case 90:
offsetX = zoomY - this.image.current.clientHeight / 2;
offsetY = this.image.current.clientWidth / 2 - zoomX;
break;
case 180:
offsetX = zoomX - this.image.current.clientWidth / 2;
offsetY = zoomY - this.image.current.clientHeight / 2;
break;
case 270:
offsetX = this.image.current.clientHeight / 2 - zoomY;
offsetY = zoomX - this.image.current.clientWidth / 2;
}
// Apply the zoom and offset
this.setState({
zoom: newZoom,
translationX: this.state.translationX + (newZoom - oldZoom) * offsetX,
translationY: this.state.translationY + (newZoom - oldZoom) * offsetY,
});
}
}
private onWheel = (ev: WheelEvent) => {
ev.stopPropagation();
ev.preventDefault();
const { deltaY } = normalizeWheelEvent(ev);
this.zoom(-(deltaY * ZOOM_COEFFICIENT));
if (ev.target === this.image.current) {
// Zoom in on the point on the image targeted by the cursor
this.zoomDelta(-deltaY * ZOOM_COEFFICIENT, ev.offsetX, ev.offsetY);
} else {
// The user is scrolling outside of the image, so we can't really
// get a targeted point. Instead, we'll just zoom in on the center.
this.zoomDelta(-deltaY * ZOOM_COEFFICIENT);
}
};
private onZoomInClick = () => {
this.zoom(ZOOM_STEP);
private onZoomInClick = (ev: MouseEvent) => {
this.zoomDelta(ZOOM_STEP);
};
private onZoomOutClick = () => {
this.zoom(-ZOOM_STEP);
private onZoomOutClick = (ev: MouseEvent) => {
this.zoomDelta(-ZOOM_STEP);
};
private onKeyDown = (ev: KeyboardEvent) => {
@ -259,7 +300,7 @@ export default class ImageView extends React.Component<IProps, IState> {
// Zoom in if we are completely zoomed out
if (this.state.zoom === this.state.minZoom) {
this.setState({ zoom: this.state.maxZoom });
this.zoom(this.state.maxZoom, ev.nativeEvent.offsetX, ev.nativeEvent.offsetY);
return;
}
@ -289,11 +330,7 @@ export default class ImageView extends React.Component<IProps, IState> {
Math.abs(this.state.translationX - this.previousX) < ZOOM_DISTANCE &&
Math.abs(this.state.translationY - this.previousY) < ZOOM_DISTANCE
) {
this.setState({
zoom: this.state.minZoom,
translationX: 0,
translationY: 0,
});
this.zoom(this.state.minZoom);
this.initX = 0;
this.initY = 0;
}