質問編集履歴
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質問内容の修正
test
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test
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Canvasに描画した画像ファイルをblob化し、axiosでPOSTの処理は以下の用に書いています、
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```javascript
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// Canvasのデータをblob化
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saveCanvas: function (canvas_id) {
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const type = "image/png";
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const canvas = document.getElementById(canvas_id);
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const dataurl = canvas.toDataURL("image/jpeg", 0.85);
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const bin = atob(dataurl.split(",")[1]);
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const buffer = new Uint8Array(bin.length);
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for (let i = 0; i < bin.length; i++) {
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buffer[i] = bin.charCodeAt(i);
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}
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const blob = new Blob([buffer.buffer], { type: type });
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const data = new FormData();
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data.append("photo", blob, "image.png"); //'photo'というkeyで保存
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},
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postCanvas: function () {
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axios
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.post("/api/photo", data, {
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headers: { "content-type": "multipart/form-data" },
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})
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.then((res) => {
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console.log("success");
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})
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.catch((error) => {
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new Error(error);
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});
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},
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```
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```javascript
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var dataurl = canvas.toDataURL("image/jpeg", 0.85);
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```
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```
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として、canvasを
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として、canvas_idを const canvasにセットしているのになぜ、「Cannot read properties of null」となってしまうのでしょうか？
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-
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vue.js 単一コンポーネント全体は以下のように書いています。
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-
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```
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<template>
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<div>
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<div id="image_area">
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<canvas ref="preview" id="preview"></canvas>
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<input type="file" name="image" accept="image/*" ref="selectimage" @change="previewImage"/>
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</div>
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<p>
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<input type="text" id="canvas_text" value="我輩は犬である" />
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<button type="button" @click="drawText('preview', 'canvas_text')">
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文字を描く
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</button>
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</p>
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<button @click="saveCanvas(),postCanvas()">アップロード</button>
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</div>
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</template>
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<script>
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export default {
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methods: {
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// canvasの画像をinput type="file"にプレビュー
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previewImage: function () {
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let file = this.$refs.selectimage.files; //ファイル情報の取得
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const canvas = this.$refs.preview; //canvasタグ
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const fileReader = new FileReader();
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fileReader.onload = function () {
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const ctx = canvas.getContext("2d");
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const image = new Image();
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image.src = fileReader.result;
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image.onload = function () {
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canvas.width = image.width;
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canvas.height = image.height;
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ctx.drawImage(image, 0, 0);
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};
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};
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fileReader.readAsDataURL(file[0]);
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},
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//キャンバスに文字を描く
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drawText: function (canvas_id, text_id) {
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const canvas = document.getElementById(canvas_id);
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const ctx = canvas.getContext("2d");
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const text = document.getElementById(text_id);
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//文字のスタイルを指定
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ctx.font = "32px serif";
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ctx.fillStyle = "#404040";
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//文字の配置を指定（左上基準にしたければtop/leftだが、文字の中心座標を指定するのでcenter
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ctx.textBaseline = "center";
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ctx.textAlign = "center";
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//座標を指定して文字を描く（座標は画像の中心に）
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const x = canvas.width / 2;
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const y = canvas.height / 2;
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ctx.fillText(text.value, x, y);
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},
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// Canvasのデータをblob化
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@@ -92,184 +268,6 @@
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},
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```
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98
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-
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99
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-
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100
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101
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-
vue.js 単一コンポーネント全体は以下のように書いています。
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102
|
-
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103
|
-
```
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104
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-
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105
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<template>
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106
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-
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107
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<div>
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<div id="image_area">
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<canvas ref="preview" id="preview"></canvas>
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<input type="file" name="image" accept="image/*" ref="selectimage" @change="previewImage"/>
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</div>
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<p>
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<input type="text" id="canvas_text" value="我輩は犬である" />
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<button type="button" @click="drawText('preview', 'canvas_text')">
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文字を描く
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</button>
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</p>
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<button @click="saveCanvas(),postCanvas()">アップロード</button>
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</div>
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</template>
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<script>
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export default {
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methods: {
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// canvasの画像をinput type="file"にプレビュー
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previewImage: function () {
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let file = this.$refs.selectimage.files; //ファイル情報の取得
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const canvas = this.$refs.preview; //canvasタグ
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const fileReader = new FileReader();
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fileReader.onload = function () {
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const ctx = canvas.getContext("2d");
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const image = new Image();
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image.src = fileReader.result;
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image.onload = function () {
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canvas.width = image.width;
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canvas.height = image.height;
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ctx.drawImage(image, 0, 0);
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};
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};
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fileReader.readAsDataURL(file[0]);
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},
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//キャンバスに文字を描く
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drawText: function (canvas_id, text_id) {
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const canvas = document.getElementById(canvas_id);
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const ctx = canvas.getContext("2d");
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const text = document.getElementById(text_id);
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//文字のスタイルを指定
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ctx.font = "32px serif";
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ctx.fillStyle = "#404040";
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-
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//文字の配置を指定（左上基準にしたければtop/leftだが、文字の中心座標を指定するのでcenter
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ctx.textBaseline = "center";
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ctx.textAlign = "center";
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//座標を指定して文字を描く（座標は画像の中心に）
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const x = canvas.width / 2;
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const y = canvas.height / 2;
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ctx.fillText(text.value, x, y);
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},
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// Canvasのデータをblob化
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saveCanvas: function (canvas_id) {
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const type = "image/png";
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const canvas = document.getElementById(canvas_id);
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const dataurl = canvas.toDataURL("image/jpeg", 0.85);
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const bin = atob(dataurl.split(",")[1]);
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const buffer = new Uint8Array(bin.length);
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for (let i = 0; i < bin.length; i++) {
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buffer[i] = bin.charCodeAt(i);
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}
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const blob = new Blob([buffer.buffer], { type: type });
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const data = new FormData();
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data.append("photo", blob, "image.png"); //'photo'というkeyで保存
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},
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postCanvas: function () {
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axios
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.post("/api/photo", data, {
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headers: { "content-type": "multipart/form-data" },
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})
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.then((res) => {
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console.log("success");
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})
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.catch((error) => {
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new Error(error);
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});
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},
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},
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};
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