From 146921ad81b5f3a8ecfc3156c317b30193a2aca5 Mon Sep 17 00:00:00 2001
From: Valentin Hervieu <valentin@hervi.eu>
Date: Sat, 8 Feb 2020 13:10:53 +0100
Subject: [PATCH] Use smaller canvas for crop demo

---
 docs/src/components/Demo/cropImage.ts | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/docs/src/components/Demo/cropImage.ts b/docs/src/components/Demo/cropImage.ts
index 734988a..e98b4f5 100644
--- a/docs/src/components/Demo/cropImage.ts
+++ b/docs/src/components/Demo/cropImage.ts
@@ -20,31 +20,42 @@ export default async function getCroppedImg(
   imageSrc: string,
   pixelCrop: Area,
   rotation = 0
-): Promise<string> {
+): Promise<string | null> {
   const image = await createImage(imageSrc)
   const canvas = document.createElement('canvas')
   const ctx = canvas.getContext('2d')
 
+  if (!ctx) {
+    return null
+  }
+
+  const maxSize = Math.max(image.width, image.height)
+  const safeArea = 2 * ((maxSize / 2) * Math.sqrt(2))
+
   // set width to double image size to allow for a safe area for the
   // image to rotate in without being clipped by canvas context
-  canvas.width = image.width * 2
-  canvas.height = image.height * 2
+  canvas.width = safeArea
+  canvas.height = safeArea
 
   // translate canvas context to a central location to allow rotating around the center.
-  ctx.translate(image.width, image.height)
+  ctx.translate(safeArea / 2, safeArea / 2)
   ctx.rotate(getRadianAngle(rotation))
-  ctx.translate(-image.width, -image.height)
+  ctx.translate(-safeArea / 2, -safeArea / 2)
 
   // draw rotated image and store data.
-  ctx.drawImage(image, image.width / 2, image.height / 2)
-  const data = ctx.getImageData(0, 0, image.width * 2, image.height * 2)
+  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, 0 - image.width / 2 - pixelCrop.x, 0 - image.height / 2 - pixelCrop.y)
+  ctx.putImageData(
+    data,
+    0 - safeArea / 2 + image.width * 0.5 - pixelCrop.x,
+    0 - safeArea / 2 + image.height * 0.5 - pixelCrop.y
+  )
 
   // As Base64 string
   // return canvas.toDataURL('image/jpeg');