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Fancy image interactions in the image viewer

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Desktop:
- Mousewheel to zoom in/out (hold ctrl to move up/down)
- If zoomed, drag around with mouse to move

Mobile:
- Move around with one finger
- Change zoom with two fingers
This commit is contained in:
Pavel Djundik 2019-10-03 16:12:49 +03:00
parent af777106bf
commit 5c4b402341
2 changed files with 325 additions and 33 deletions
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321
client/components/ImageViewer.vue
View file

@ -1,23 +1,25 @@
<template>
<div id="image-viewer" ref="viewer" :class="{opened: link !== null}" @click="closeViewer">
<div
id="image-viewer"
ref="viewer"
:class="{opened: link !== null}"
@wheel="onMouseWheel"
@touchstart.passive="onTouchStart"
@click="onClick"
>
<template v-if="link !== null">
<button class="close-btn" aria-label="Close"></button>
<a class="open-btn" :href="link.link" target="_blank" rel="noopener"></a>
<!--button
v-if="hasPreviousImage"
class="previous-image-btn"
aria-label="Previous image"
></button>
<button v-if="hasNextImage" class="next-image-btn" aria-label="Next image"></button-->
<a class="image-link" :href="link.link" target="_blank">
<img :src="link.thumb" decoding="async" alt="" />
</a>
<a class="btn open-btn" :href="link.link" target="_blank">
<span v-if="link.type == 'image'">Open image</span>
<span v-else>Visit page</span>
</a>
<img
ref="image"
:src="link.thumb"
alt=""
:style="computeImageStyles"
@load="onImageLoad"
@mousedown="onImageMouseDown"
@touchstart.passive="onImageTouchStart"
/>
</template>
</div>
</template>
@ -28,6 +30,15 @@ export default {
data() {
return {
link: null,
position: {
x: 0,
y: 0,
},
transform: {
x: 0,
y: 0,
scale: 0,
},
};
},
computed: {
@ -42,6 +53,11 @@ export default {
watch: {
link() {
// TODO: history.pushState
if (this.link === null) {
return;
}
this.$root.$on("resize", this.correctPosition);
},
},
mounted() {
@ -53,8 +69,281 @@ export default {
},
methods: {
closeViewer() {
this.$root.$off("resize", this.correctPosition);
this.link = null;
},
onImageLoad() {
this.prepareImage();
},
prepareImage() {
const viewer = this.$refs.viewer;
const image = this.$refs.image;
const width = viewer.offsetWidth;
const height = viewer.offsetHeight;
const scale = Math.min(1, width / image.width, height / image.height);
this.position.x = -image.naturalWidth / 2;
this.position.y = -image.naturalHeight / 2;
this.transform.scale = Math.max(scale, 0.1);
this.transform.x = width / 2;
this.transform.y = height / 2;
},
calculateZoomShift(newScale, x, y, oldScale) {
const imageWidth = this.$refs.image.width;
const centerX = this.$refs.viewer.offsetWidth / 2;
const centerY = this.$refs.viewer.offsetHeight / 2;
return {
x:
centerX -
((centerX - (y - (imageWidth * x) / 2)) / x) * newScale +
(imageWidth * newScale) / 2,
y:
centerY -
((centerY - (oldScale - (imageWidth * x) / 2)) / x) * newScale +
(imageWidth * newScale) / 2,
};
},
correctPosition() {
const image = this.$refs.image;
const widthScaled = image.width * this.transform.scale;
const heightScaled = image.height * this.transform.scale;
const containerWidth = this.$refs.viewer.offsetWidth;
const containerHeight = this.$refs.viewer.offsetHeight;
if (widthScaled < containerWidth) {
this.transform.x = containerWidth / 2;
} else if (this.transform.x - widthScaled / 2 > 0) {
this.transform.x = widthScaled / 2;
} else if (this.transform.x + widthScaled / 2 < containerWidth) {
this.transform.x = containerWidth - widthScaled / 2;
}
if (heightScaled < containerHeight) {
this.transform.y = containerHeight / 2;
} else if (this.transform.y - heightScaled / 2 > 0) {
this.transform.y = heightScaled / 2;
} else if (this.transform.y + heightScaled / 2 < containerHeight) {
this.transform.y = containerHeight - heightScaled / 2;
}
},
// Reduce multiple touch points into a single x/y/scale
reduceTouches(touches) {
let totalX = 0;
let totalY = 0;
let totalScale = 0;
for (let i = 0; i < touches.length; i++) {
const x = touches[i].clientX;
const y = touches[i].clientY;
totalX += x;
totalY += y;
for (let i2 = 0; i2 < touches.length; i2++) {
if (i !== i2) {
const x2 = touches[i2].clientX;
const y2 = touches[i2].clientY;
totalScale += Math.sqrt((x - x2) * (x - x2) + (y - y2) * (y - y2));
}
}
}
if (totalScale === 0) {
totalScale = 1;
}
return {
x: totalX / touches.length,
y: totalY / touches.length,
scale: totalScale / touches.length,
};
},
onTouchStart(e) {
// prevent sidebar touchstart event, we don't want to interact with sidebar while in image viewer
e.stopImmediatePropagation();
},
// Touch image manipulation:
// 1. Move around by dragging it with one finger
// 2. Change image scale by using two fingers
onImageTouchStart(e) {
const image = this.$refs.image;
let touch = this.reduceTouches(e.touches);
let currentTouches = e.touches;
let touchEndFingers = 0;
const currentTransform = {
x: touch.x,
y: touch.y,
scale: touch.scale,
};
const startTransform = {
x: this.transform.x,
y: this.transform.y,
scale: this.transform.scale,
};
const touchMove = (moveEvent) => {
touch = this.reduceTouches(moveEvent.touches);
// TODO: There's bugs with multi finger interactions, needs more testing
if (currentTouches.length !== moveEvent.touches.length) {
currentTransform.x = touch.x;
currentTransform.y = touch.y;
currentTransform.scale = touch.scale;
startTransform.x = this.transform.x;
startTransform.y = this.transform.y;
startTransform.scale = this.transform.scale;
}
const deltaX = touch.x - currentTransform.x;
const deltaY = touch.y - currentTransform.y;
const deltaScale = touch.scale / currentTransform.scale;
currentTouches = moveEvent.touches;
touchEndFingers = 0;
const newScale = Math.min(3, Math.max(0.1, startTransform.scale * deltaScale));
const fixedPosition = this.calculateZoomShift(
newScale,
startTransform.scale,
startTransform.x,
startTransform.y
);
if (newScale > 1) {
this.transform.x = fixedPosition.x + deltaX;
this.transform.y = fixedPosition.y + deltaY;
} else if (Math.abs(deltaX) > Math.abs(deltaY)) {
this.transform.x = fixedPosition.x + deltaX;
} else {
this.transform.y = fixedPosition.y + deltaY;
}
this.transform.scale = newScale;
};
const touchEnd = (endEvent) => {
const changedTouches = endEvent.changedTouches.length;
if (currentTouches.length > changedTouches + touchEndFingers) {
touchEndFingers += changedTouches;
return;
}
// todo: this is swipe to close, but it's not working very well due to unfinished delta calculation
/* if (
this.transform.scale <= 1 &&
endEvent.changedTouches[0].clientY - startTransform.y <= -70
) {
return this.closeViewer();
}*/
this.correctPosition();
image.removeEventListener("touchmove", touchMove, {passive: true});
image.removeEventListener("touchend", touchEnd, {passive: true});
};
image.addEventListener("touchmove", touchMove, {passive: true});
image.addEventListener("touchend", touchEnd, {passive: true});
},
// Image mouse manipulation:
// 1. Mouse wheel scrolling will zoom in and out
// 2. If image is zoomed in, simply dragging it will move it around
onImageMouseDown(e) {
// todo: ignore if in touch event currently?
// only left mouse
if (e.which !== 1) {
return;
}
e.stopPropagation();
e.preventDefault();
const viewer = this.$refs.viewer;
const image = this.$refs.image;
const startX = e.clientX;
const startY = e.clientY;
const startTransformX = this.transform.x;
const startTransformY = this.transform.y;
const widthScaled = image.width * this.transform.scale;
const heightScaled = image.height * this.transform.scale;
const containerWidth = viewer.offsetWidth;
const containerHeight = viewer.offsetHeight;
const centerX = this.transform.x - widthScaled / 2;
const centerY = this.transform.y - heightScaled / 2;
let movedDistance = 0;
const mouseMove = (moveEvent) => {
moveEvent.stopPropagation();
moveEvent.preventDefault();
const newX = moveEvent.clientX - startX;
const newY = moveEvent.clientY - startY;
movedDistance = Math.max(movedDistance, Math.abs(newX), Math.abs(newY));
if (centerX < 0 || widthScaled + centerX > containerWidth) {
this.transform.x = startTransformX + newX;
}
if (centerY < 0 || heightScaled + centerY > containerHeight) {
this.transform.y = startTransformY + newY;
}
};
const mouseUp = (upEvent) => {
this.correctPosition();
if (movedDistance < 2 && upEvent.button === 0) {
this.closeViewer();
}
image.removeEventListener("mousemove", mouseMove);
image.removeEventListener("mouseup", mouseUp);
};
image.addEventListener("mousemove", mouseMove);
image.addEventListener("mouseup", mouseUp);
},
// If image is zoomed in, holding ctrl while scrolling will move the image up and down
onMouseWheel(e) {
// if image viewer is closing (css animation), you can still trigger mousewheel
// TODO: Figure out a better fix for this
if (this.link === null) {
return;
}
e.preventDefault(); // TODO: Can this be passive?
if (e.ctrlKey) {
this.transform.y += e.deltaY;
} else {
const delta = e.deltaY > 0 ? 0.1 : -0.1;
const newScale = Math.min(3, Math.max(0.1, this.transform.scale + delta));
const fixedPosition = this.calculateZoomShift(
newScale,
this.transform.scale,
this.transform.x,
this.transform.y
);
this.transform.scale = newScale;
this.transform.x = fixedPosition.x;
this.transform.y = fixedPosition.y;
}
this.correctPosition();
},
onClick(e) {
// If click triggers on the image, ignore it
if (e.target === this.$refs.image) {
return;
}
this.closeViewer();
},
},
};
</script>

37
client/css/style.css
View file

@ -278,6 +278,7 @@ kbd {
#help .report-issue-link::before,
#image-viewer .previous-image-btn::before,
#image-viewer .next-image-btn::before,
#image-viewer .open-btn::before,
#sidebar .not-secure-icon::before,
#sidebar .not-connected-icon::before,
#sidebar .parted-channel-icon::before,
@ -477,6 +478,10 @@ kbd {
content: "\f105"; /* http://fontawesome.io/icon/angle-right/ */
}
#image-viewer .open-btn::before {
content: "\f35d"; /* https://fontawesome.com/icons/external-link-alt?style=solid */
}
/* End icons */
#viewport {
@ -2616,6 +2621,7 @@ part/quit messages where we don't load previews (adds a blank line otherwise) */
#upload-overlay,
#image-viewer,
#image-viewer .open-btn,
#image-viewer .close-btn {
/* Vertically and horizontally center stuff */
display: flex;
@ -2636,6 +2642,7 @@ part/quit messages where we don't load previews (adds a blank line otherwise) */
opacity: 0;
transition: opacity 0.2s, visibility 0.2s;
z-index: 999;
user-select: none;
}
#image-viewer.opened {
@ -2649,6 +2656,7 @@ part/quit messages where we don't load previews (adds a blank line otherwise) */
}
#image-viewer .close-btn,
#image-viewer .open-btn,
#image-viewer .previous-image-btn,
#image-viewer .next-image-btn {
position: fixed;
@ -2670,6 +2678,14 @@ part/quit messages where we don't load previews (adds a blank line otherwise) */
content: "×";
}
#image-viewer .open-btn {
right: 0;
bottom: 0;
top: auto;
height: 2em;
z-index: 1002;
}
#image-viewer .previous-image-btn,
#image-viewer .next-image-btn {
bottom: 0;
@ -2690,19 +2706,10 @@ part/quit messages where we don't load previews (adds a blank line otherwise) */
opacity: 1;
}
#image-viewer .image-link {
margin: 10px;
}
#image-viewer .image-link:hover {
opacity: 1;
}
#image-viewer .image-link img {
max-width: 100%;
/* Top/Bottom margins + button height + image/button margin */
max-height: calc(100vh - 2 * 10px - 37px - 10px);
#image-viewer > img {
cursor: grab;
position: absolute;
transform-origin: 50% 50%;
/* Checkered background for transparent images */
background-position: 0 0, 10px 10px;
@ -2712,10 +2719,6 @@ part/quit messages where we don't load previews (adds a blank line otherwise) */
linear-gradient(45deg, #eee 25%, #fff 25%, #fff 75%, #eee 75%, #eee 100%);
}
#image-viewer .open-btn {
margin: 0 auto 10px;
}
/* Correctly handle multiple successive whitespace characters.
For example: user has quit ( ===> L O L <=== ) */