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Experimental: Add scale-down image mode with DPR sizing #87

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Experimental: Add scale-down image mode with DPR sizing #87

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64 changes: 56 additions & 8 deletions src/routes/components/Image.svelte
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Original file line number Diff line number Diff line change
Expand Up @@ -50,15 +50,59 @@
return variant_entries.join(', ');
}

// Apply scale to image
let image_style = $derived(`
object-position: ${node.focal_point_x * 100}% ${node.focal_point_y * 100}%;
transform: scale(${node.scale});
transform-origin: ${node.focal_point_x * 100}% ${node.focal_point_y * 100}%;
object-fit: ${node.object_fit};
`);
let is_scale_down = $derived(node.object_fit === 'scale-down');

// For scale-down: cap the img element to its DPR-corrected natural size
// and position it within the parent using the focal point.
// SVGs don't need DPR correction since they scale cleanly.
let dpr = $derived(typeof window !== 'undefined' ? window.devicePixelRatio : 2);

let css_natural_width = $derived(
is_scale_down && node.width && !is_svg
? Math.round(node.width / dpr)
: undefined
);

let css_natural_height = $derived(
is_scale_down && node.height && !is_svg
? Math.round(node.height / dpr)
: undefined
);

// Apply scale to image
let image_style = $derived.by(() => {
if (is_scale_down) {
// Position the img absolutely within the overflow-hidden parent.
// left/top set by focal point %, translate pulls it back so the
// focal point itself lands at that position — same trick as
// background-position semantics.
let parts = [
`position: absolute`,
`left: ${node.focal_point_x * 100}%`,
`top: ${node.focal_point_y * 100}%`,
`translate: ${-node.focal_point_x * 100}% ${-node.focal_point_y * 100}%`,
`transform: scale(${node.scale})`,
`transform-origin: ${node.focal_point_x * 100}% ${node.focal_point_y * 100}%`,
`object-fit: contain`
];

if (css_natural_width !== undefined) {
parts.push(`max-width: ${css_natural_width}px`);
}
if (css_natural_height !== undefined) {
parts.push(`max-height: ${css_natural_height}px`);
}

return parts.join('; ') + ';';
}

return [
`object-position: ${node.focal_point_x * 100}% ${node.focal_point_y * 100}%`,
`transform: scale(${node.scale})`,
`transform-origin: ${node.focal_point_x * 100}% ${node.focal_point_y * 100}%`,
`object-fit: ${node.object_fit}`
].join('; ') + ';';
});
</script>

{#if display_src}
Expand All @@ -70,6 +114,7 @@
alt={node.alt}
width={node.width}
height={node.height}
class:scale-down-mode={is_scale_down}
style={image_style}
/>
{/if}
Expand All @@ -81,5 +126,8 @@
transform-origin: center center;
}


img.scale-down-mode {
width: auto;
height: auto;
}
</style>
10 changes: 6 additions & 4 deletions src/routes/components/MediaControls.svelte
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Original file line number Diff line number Diff line change
Expand Up @@ -71,12 +71,14 @@
e.preventDefault();
}

const OBJECT_FIT_MODES = ['cover', 'contain', 'scale-down'];

function handle_double_click(e) {
const current_index = OBJECT_FIT_MODES.indexOf(media_node.object_fit);
const next_index = (current_index + 1) % OBJECT_FIT_MODES.length;
const tr = svedit.session.tr;
tr.set([...path, 'scale'], MIN_SCALE);
// tr.set([...path, 'focal_point_x'], 0.5);
// tr.set([...path, 'focal_point_y'], 0.5);
tr.set([...path, 'object_fit'], media_node.object_fit === 'cover' ? 'contain' : 'cover');
tr.set([...path, 'object_fit'], OBJECT_FIT_MODES[next_index]);
svedit.session.apply(tr, { batch: true });
}

Expand Down Expand Up @@ -192,4 +194,4 @@
background: var(--svedit-editing-stroke);
transform: translate(-50%, -50%);
}
</style>
</style>