dify/web/app/components/base/app-icon-picker/utils.ts

export const createImage = (url: string) =>
  new Promise<HTMLImageElement>((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 function getRadianAngle(degreeValue: number) {
  return (degreeValue * Math.PI) / 180
}

export function getMimeType(fileName: string): string {
  const extension = fileName.split('.').pop()?.toLowerCase()
  switch (extension) {
    case 'png':
      return 'image/png'
    case 'jpg':
    case 'jpeg':
      return 'image/jpeg'
    case 'gif':
      return 'image/gif'
    case 'webp':
      return 'image/webp'
    default:
      return 'image/jpeg'
  }
}

/**
 * Returns the new bounding area of a rotated rectangle.
 */
export function rotateSize(width: number, height: number, rotation: number) {
  const rotRad = getRadianAngle(rotation)

  return {
    width:
            Math.abs(Math.cos(rotRad) * width) + Math.abs(Math.sin(rotRad) * height),
    height:
            Math.abs(Math.sin(rotRad) * width) + Math.abs(Math.cos(rotRad) * height),
  }
}

/**
 * This function was adapted from the one in the ReadMe of https://github.com/DominicTobias/react-image-crop
 */
export default async function getCroppedImg(
  imageSrc: string,
  pixelCrop: { x: number; y: number; width: number; height: number },
  fileName: string,
  rotation = 0,
  flip = { horizontal: false, vertical: false },
): Promise<Blob> {
  const image = await createImage(imageSrc)
  const canvas = document.createElement('canvas')
  const ctx = canvas.getContext('2d')
  const mimeType = getMimeType(fileName)

  if (!ctx)
    throw new Error('Could not create a canvas context')

  const rotRad = getRadianAngle(rotation)

  // calculate bounding box of the rotated image
  const { width: bBoxWidth, height: bBoxHeight } = rotateSize(
    image.width,
    image.height,
    rotation,
  )

  // set canvas size to match the bounding box
  canvas.width = bBoxWidth
  canvas.height = bBoxHeight

  // translate canvas context to a central location to allow rotating and flipping around the center
  ctx.translate(bBoxWidth / 2, bBoxHeight / 2)
  ctx.rotate(rotRad)
  ctx.scale(flip.horizontal ? -1 : 1, flip.vertical ? -1 : 1)
  ctx.translate(-image.width / 2, -image.height / 2)

  // draw rotated image
  ctx.drawImage(image, 0, 0)

  const croppedCanvas = document.createElement('canvas')

  const croppedCtx = croppedCanvas.getContext('2d')

  if (!croppedCtx)
    throw new Error('Could not create a canvas context')

  // Set the size of the cropped canvas
  croppedCanvas.width = pixelCrop.width
  croppedCanvas.height = pixelCrop.height

  // Draw the cropped image onto the new canvas
  croppedCtx.drawImage(
    canvas,
    pixelCrop.x,
    pixelCrop.y,
    pixelCrop.width,
    pixelCrop.height,
    0,
    0,
    pixelCrop.width,
    pixelCrop.height,
  )

  return new Promise((resolve, reject) => {
    croppedCanvas.toBlob((file) => {
      if (file)
        resolve(file)
      else
        reject(new Error('Could not create a blob'))
    }, mimeType)
  })
}