1 files changed, 54 insertions, 0 deletions
diff --git a/src/components/AvatarCrop/canvasUtils.js b/src/components/AvatarCrop/canvasUtils.js
new file mode 100644
index 0000000..b01aadc
--- /dev/null
+++ b/src/components/AvatarCrop/canvasUtils.js
@@ -0,0 +1,54 @@
+const createImage = url =>
+  new Promise((resolve, reject) => {
+    const image = new Image();
+    image.addEventListener('load', () => resolve(image));
+    image.addEventListener('error', error => reject(error));
+    image.setAttribute('crossOrigin', 'anonymous') ;// needed to avoid cross-origin issues on CodeSandbox
+    image.src = url
+  });
+
+export async function getCroppedImg(imageSrc, pixelCrop) {
+  const image = await createImage(imageSrc);
+  const canvas = document.createElement('canvas');
+  const ctx = canvas.getContext('2d');
+
+  const maxSize = Math.max(image.width, image.height);
+  const safeArea = 2 * ((maxSize / 2) * Math.sqrt(2));
+
+  // set each dimensions to double largest dimension to allow for a safe area for the
+  // image to rotate in without being clipped by canvas context
+  canvas.width = safeArea;
+  canvas.height = safeArea;
+
+  // translate canvas context to a central location on image to allow rotating around the center.
+  ctx.translate(safeArea / 2, safeArea / 2);
+  ctx.translate(-safeArea / 2, -safeArea / 2);
+
+  // draw rotated image and store data.
+  ctx.drawImage(
+    image,
+    safeArea / 2 - image.width * 0.5,
+    safeArea / 2 - image.height * 0.5
+  );
+  const data = ctx.getImageData(0, 0, safeArea, safeArea);
+
+  // set canvas width to final desired crop size - this will clear existing context
+  canvas.width = pixelCrop.width;
+  canvas.height = pixelCrop.height;
+
+  // paste generated rotate image with correct offsets for x,y crop values.
+  ctx.putImageData(
+    data,
+    Math.round(0 - safeArea / 2 + image.width * 0.5 - pixelCrop.x),
+    Math.round(0 - safeArea / 2 + image.height * 0.5 - pixelCrop.y)
+  );
+
+  // As Base64 string
+  // return canvas.toDataURL('image/jpeg');
+
+  // As a blob
+
+  return new Promise(resolve => {
+    canvas.toBlob(file => resolve(file))
+  })
+}