58 lines
1.9 KiB
TypeScript
58 lines
1.9 KiB
TypeScript
const MAX_IMAGE_SIZE = 512;
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export type Area = {
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width: number;
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height: number;
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x: number;
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y: number;
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};
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const createImage = (url: string) =>
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new Promise<HTMLImageElement>((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 async function getCroppedImg(imageSrc: string, pixelCrop: Area): Promise<string> {
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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) throw new Error("Context is null, this should never happen.");
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const maxSize = Math.max(image.naturalWidth, image.naturalHeight);
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const resizeRatio = MAX_IMAGE_SIZE / maxSize < 1 ? Math.max(MAX_IMAGE_SIZE / maxSize, 0.75) : 1;
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// huh, what? - Having this turned off actually improves image quality as otherwise anti-aliasing is applied
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// this reduces the quality of the image overall because it anti-aliases the existing, copied image; blur results
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ctx.imageSmoothingEnabled = false;
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// pixelCrop is always 1:1 - width = height
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canvas.width = canvas.height = Math.min(maxSize * resizeRatio, pixelCrop.width);
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ctx.drawImage(
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image,
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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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0,
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0,
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canvas.width,
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canvas.height
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);
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// on very low ratios, the quality of the resize becomes awful. For this reason the resizeRatio is limited to 0.75
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if (resizeRatio <= 0.75) {
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// With a smaller image, thus improved ratio. Keep doing this until the resizeRatio > 0.75.
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return getCroppedImg(canvas.toDataURL("image/jpeg"), {
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width: canvas.width,
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height: canvas.height,
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x: 0,
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y: 0,
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});
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}
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return canvas.toDataURL("image/jpeg");
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}
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