90 lines
2.7 KiB
TypeScript
90 lines
2.7 KiB
TypeScript
export const createImage = (url: string): Promise<HTMLImageElement> =>
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new Promise((resolve, reject) => {
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const image = new Image()
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image.addEventListener('load', () => resolve(image))
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image.addEventListener('error', (error) => reject(error))
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image.setAttribute('crossOrigin', 'anonymous') // needed to avoid cross-origin issues on CodeSandbox
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image.src = url
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})
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export function getRadianAngle(degreeValue: number) {
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return (degreeValue * Math.PI) / 180
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}
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/**
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* Returns the new bounding area of a rotated rectangle.
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*/
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export function rotateSize(width: number, height: number, rotation: number) {
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const rotRad = getRadianAngle(rotation)
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return {
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width:
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Math.abs(Math.cos(rotRad) * width) + Math.abs(Math.sin(rotRad) * height),
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height:
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Math.abs(Math.sin(rotRad) * width) + Math.abs(Math.cos(rotRad) * height),
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}
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}
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/**
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* This function was adapted from the one in the ReadMe of https://github.com/DominicTobias/react-image-crop
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*/
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export async function getCroppedImg(
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imageSrc: string,
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pixelCrop: { x: number; y: number; width: number; height: number },
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rotation = 0,
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flip = { horizontal: false, vertical: false }
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): Promise<Blob | null> {
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const image = await createImage(imageSrc)
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const canvas = document.createElement('canvas')
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const ctx = canvas.getContext('2d')
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if (!ctx) {
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return null
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}
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const rotRad = getRadianAngle(rotation)
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// calculate bounding box of the rotated image
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const { width: bBoxWidth, height: bBoxHeight } = rotateSize(
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image.width,
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image.height,
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rotation
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)
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// set canvas size to match the bounding box
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canvas.width = bBoxWidth
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canvas.height = bBoxHeight
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// translate canvas context to a central location to allow rotating and flipping around the center
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ctx.translate(bBoxWidth / 2, bBoxHeight / 2)
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ctx.rotate(rotRad)
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ctx.scale(flip.horizontal ? -1 : 1, flip.vertical ? -1 : 1)
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ctx.translate(-image.width / 2, -image.height / 2)
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// draw rotated image
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ctx.drawImage(image, 0, 0)
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// croppedAreaPixels values are bounding box relative
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// extract the cropped image using these values
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const data = ctx.getImageData(
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pixelCrop.x,
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pixelCrop.y,
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pixelCrop.width,
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pixelCrop.height
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)
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// set canvas width to final desired crop size - this will clear existing context
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canvas.width = pixelCrop.width
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canvas.height = pixelCrop.height
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// paste generated rotate image at the top left corner
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ctx.putImageData(data, 0, 0)
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// As a Blob
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return new Promise((resolve) => {
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canvas.toBlob((file) => {
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resolve(file)
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}, 'image/jpeg')
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})
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}
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