58 lines
1.7 KiB
Dart
58 lines
1.7 KiB
Dart
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import 'dart:math' as math;
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import 'dart:ui';
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/// Shared capture guide geometry (same as the on-screen shooting frame).
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class GuideFrame {
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static const double aspect = 63 / 88;
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static const double maxHeightFraction = 0.62;
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static const double maxWidthFraction = 0.78;
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static const double centerYFraction = 0.46;
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/// Guide rect inside a viewport (preview overlay coordinates).
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static Rect inViewport(Size size) {
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final maxH = size.height * maxHeightFraction;
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final maxW = size.width * maxWidthFraction;
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var h = maxH;
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var w = h * aspect;
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if (w > maxW) {
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w = maxW;
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h = w / aspect;
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}
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return Rect.fromCenter(
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center: Offset(size.width / 2, size.height * centerYFraction),
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width: w,
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height: h,
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);
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}
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/// Map the viewport guide into image pixels when the image is shown with
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/// [BoxFit.cover] in [viewport] (camera preview).
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static Rect inCoverImage({
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required Size viewport,
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required Size imageSize,
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}) {
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final guide = inViewport(viewport);
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final scale = math.max(
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viewport.width / imageSize.width,
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viewport.height / imageSize.height,
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);
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final dispW = imageSize.width * scale;
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final dispH = imageSize.height * scale;
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final ox = (viewport.width - dispW) / 2;
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final oy = (viewport.height - dispH) / 2;
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final mapped = Rect.fromLTRB(
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(guide.left - ox) / scale,
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(guide.top - oy) / scale,
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(guide.right - ox) / scale,
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(guide.bottom - oy) / scale,
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);
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return mapped.intersect(
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Rect.fromLTWH(0, 0, imageSize.width, imageSize.height),
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);
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}
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/// Guide applied directly in image space (gallery / no viewport).
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static Rect inImage(Size imageSize) => inViewport(imageSize);
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}
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