initiatived21/d21

/**
 *  Synchronous function
 *  Crop image function
 *  Used for image crop tool
 *
 *  https://gist.github.com/DominicTobias/b1fb501349893922ec7f
 *
 *  Returns image data uri, not the loaded image
 */

function cropImage(originalImg, crop, maxWidth, maxHeight) {
  const
    imageWidth = originalImg.naturalWidth,
    imageHeight = originalImg.naturalHeight,

    cropX = Math.round((crop.x / 100) * imageWidth),
    cropY = Math.round((crop.y / 100) * imageHeight),

    cropWidth = Math.round((crop.width / 100) * imageWidth),
    cropHeight = Math.round((crop.height / 100) * imageHeight)

  let
    destWidth = cropWidth,
    destHeight = cropHeight

  if (maxWidth || maxHeight) {
    // Scale the crop.
    const scaledCrop = scale({
      width: cropWidth,
      height: cropHeight,
      maxWidth: maxWidth,
      maxHeight: maxHeight
    })

    /* NEVER USED: Waiting for answer from original author on why it's in it. */
    // Scale the image based on the crop scale.
    // const scaledImage = scale({
    //   scale: scaledCrop.scale,
    //   width: imageWidth,
    //   height: imageHeight
    // })

    destWidth = Math.round(scaledCrop.width)
    destHeight = Math.round(scaledCrop.height)
  }

  const canvas = document.createElement('canvas')
  canvas.width = destWidth
  canvas.height = destHeight

  const ctx = canvas.getContext('2d')

  ctx.drawImage(originalImg, cropX, cropY, cropWidth, cropHeight, 0, 0, destWidth, destHeight)

  const imgDest = canvas.toDataURL('image/jpeg')

  return imgDest
}

function scale(options) {
  let scale = options.scale ||
    Math.min(options.maxWidth/options.width, options.maxHeight/options.height)

  scale = Math.min(scale, options.maxScale || 1)

  return {
    scale,
    width: options.width * scale,
    height: options.height * scale
  }
}

export default cropImage