Implemented sprite resizing

js/_pixelEditorUtility.js

@@ -105,4 +105,81 @@ function getElementAbsolutePosition(element) {
 	}
 
 	return [curleft,curtop];
-}
+}
+
+function nearestNeighbor (src, dst) {
+	let pos = 0
+
+	for (let y = 0; y < dst.height; y++) {
+		for (let x = 0; x < dst.width; x++) {
+		const srcX = Math.floor(x * src.width / dst.width)
+		const srcY = Math.floor(y * src.height / dst.height)
+
+		let srcPos = ((srcY * src.width) + srcX) * 4
+
+		dst.data[pos++] = src.data[srcPos++] // R
+		dst.data[pos++] = src.data[srcPos++] // G
+		dst.data[pos++] = src.data[srcPos++] // B
+		dst.data[pos++] = src.data[srcPos++] // A
+		}
+	}
+}
+  
+function bilinearInterpolation (src, dst) {
+	function interpolate (k, kMin, kMax, vMin, vMax) {
+	  	return Math.round((k - kMin) * vMax + (kMax - k) * vMin)
+	}
+  
+	function interpolateHorizontal (offset, x, y, xMin, xMax) {
+	  	const vMin = src.data[((y * src.width + xMin) * 4) + offset]
+	  	if (xMin === xMax) return vMin
+  
+	  	const vMax = src.data[((y * src.width + xMax) * 4) + offset]
+	  	return interpolate(x, xMin, xMax, vMin, vMax)
+	}
+  
+	function interpolateVertical (offset, x, xMin, xMax, y, yMin, yMax) {
+	  	const vMin = interpolateHorizontal(offset, x, yMin, xMin, xMax)
+	  	if (yMin === yMax) return vMin
+  
+	  	const vMax = interpolateHorizontal(offset, x, yMax, xMin, xMax)
+	  	return interpolate(y, yMin, yMax, vMin, vMax)
+	}
+  
+	let pos = 0
+  
+	for (let y = 0; y < dst.height; y++) {
+	  	for (let x = 0; x < dst.width; x++) {
+			const srcX = x * src.width / dst.width
+			const srcY = y * src.height / dst.height
+	
+			const xMin = Math.floor(srcX)
+			const yMin = Math.floor(srcY)
+	
+			const xMax = Math.min(Math.ceil(srcX), src.width - 1)
+			const yMax = Math.min(Math.ceil(srcY), src.height - 1)
+	
+			dst.data[pos++] = interpolateVertical(0, srcX, xMin, xMax, srcY, yMin, yMax) // R
+			dst.data[pos++] = interpolateVertical(1, srcX, xMin, xMax, srcY, yMin, yMax) // G
+			dst.data[pos++] = interpolateVertical(2, srcX, xMin, xMax, srcY, yMin, yMax) // B
+			dst.data[pos++] = interpolateVertical(3, srcX, xMin, xMax, srcY, yMin, yMax) // A
+		}
+	}
+}
+  
+function resizeImageData (image, width, height, algorithm) {
+	algorithm = algorithm || 'bilinear-interpolation'
+  
+	let resize
+	switch (algorithm) {
+	  	case 'nearest-neighbor': resize = nearestNeighbor; break
+	  	case 'bilinear-interpolation': resize = bilinearInterpolation; break
+	  	default: throw new Error(`Unknown algorithm: ${algorithm}`)
+	}
+  
+	const result = new ImageData(width, height)
+  
+	resize(image, result)
+  
+	return result
+  }