質問編集履歴
1
ソースコードの引用
test
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File without changes
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test
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@@ -19,3 +19,107 @@
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よろしくお願いします。
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追記（上記のデモサイトから引用させていただきました）
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```HTML/JavaScript
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>JS Bin</title>
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</head>
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<body>
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<input type="file" onchange="onInputChanged(event)">
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<hr>オリジナルサイズ:<br>
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<img id="previewLarge">
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<hr>縮小サイズ:<br>
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<img id="previewSmall">
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<script>
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function onInputChanged(e) {
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var file = e.target.files && e.target.files[0];
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if (file != null) {
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var reader = new FileReader();
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reader.onload = onImageLoad;
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reader.readAsDataURL(file);
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}
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}
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function onImageLoad(e) {
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var largeData = e.target.result;
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var smallData = makeSmall(largeData);
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previewLarge.src = largeData;
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previewSmall.src = smallData;
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}
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// 画像データ(DataURL)を縮小して返す
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function makeSmall(data) {
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// 画像データの縦横サイズを取得する
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var image = document.createElement('img');
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image.src = data;
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var width = image.naturalWidth;
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var height = image.naturalHeight;
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// 縮小する。今回は縦横それぞれ1/2
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var canvas = document.createElement('canvas');
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canvas.width = width / 2;
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canvas.height = height / 2;
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canvas.getContext("2d").drawImage(image, 0, 0, width / 2, height / 2);
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return canvas.toDataURL();
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}
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</script>
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</body>
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</html>
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```
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