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//
// ImageUtils.swift
// iTexSnip
//
// Created by Navan Chauhan on 10/13/24.
//
import AppKit
import CoreImage
import Foundation
let IMAGE_MEAN: CGFloat = 0.9545467
let IMAGE_STD: CGFloat = 0.15394445
let FIXED_IMG_SIZE: CGFloat = 448
let IMG_CHANNELS: Int = 1
let MIN_HEIGHT: CGFloat = 12
let MIN_WIDTH: CGFloat = 30
// Load image from URL
func loadImage(from urlString: String) -> NSImage? {
guard let url = URL(string: urlString), let imageData = try? Data(contentsOf: url) else {
return nil
}
return NSImage(data: imageData)
}
// Helper to convert NSImage to CIImage
func nsImageToCIImage(_ image: NSImage) -> CIImage? {
guard let data = image.tiffRepresentation,
let bitmapImage = NSBitmapImageRep(data: data),
let cgImage = bitmapImage.cgImage
else {
return nil
}
return CIImage(cgImage: cgImage)
}
func trimWhiteBorder(image: CIImage) -> CIImage? {
let context = CIContext()
// Render the CIImage to a CGImage for pixel analysis
guard let cgImage = context.createCGImage(image, from: image.extent) else {
return nil
}
// Access the pixel data
let width = cgImage.width
let height = cgImage.height
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bytesPerPixel = 4
let bytesPerRow = bytesPerPixel * width
let bitmapInfo = CGImageAlphaInfo.premultipliedLast.rawValue
var pixelData = [UInt8](repeating: 0, count: height * bytesPerRow)
guard
let contextRef = CGContext(
data: &pixelData,
width: width,
height: height,
bitsPerComponent: 8,
bytesPerRow: bytesPerRow,
space: colorSpace,
bitmapInfo: bitmapInfo
)
else {
return nil
}
contextRef.draw(cgImage, in: CGRect(x: 0, y: 0, width: CGFloat(width), height: CGFloat(height)))
// Define the white color in RGBA
let whitePixel: [UInt8] = [255, 255, 255, 255]
var minX = width
var minY = height
var maxX: Int = 0
var maxY: Int = 0
// Scan the pixels to find the bounding box of non-white content
for y in 0..<height {
for x in 0..<width {
let pixelIndex = (y * bytesPerRow) + (x * bytesPerPixel)
let pixel = Array(pixelData[pixelIndex..<(pixelIndex + 4)])
if pixel != whitePixel {
if x < minX { minX = x }
if x > maxX { maxX = x }
if y < minY { minY = y }
if y > maxY { maxY = y }
}
}
}
// If no non-white content was found, return the original image
if minX == width || minY == height || maxX == 0 || maxY == 0 {
return image
}
// Compute the bounding box and crop the image
let croppedRect = CGRect(
x: CGFloat(minX), y: CGFloat(minY), width: CGFloat(maxX - minX), height: CGFloat(maxY - minY))
return image.cropped(to: croppedRect)
}
// Padding image with white border
func addWhiteBorder(to image: CIImage, maxSize: CGFloat) -> CIImage {
let randomPadding = (0..<4).map { _ in CGFloat(arc4random_uniform(UInt32(maxSize))) }
var xPadding = randomPadding[0] + randomPadding[2]
var yPadding = randomPadding[1] + randomPadding[3]
// Ensure the minimum width and height
if xPadding + image.extent.width < MIN_WIDTH {
let compensateWidth = (MIN_WIDTH - (xPadding + image.extent.width)) * 0.5 + 1
xPadding += compensateWidth
}
if yPadding + image.extent.height < MIN_HEIGHT {
let compensateHeight = (MIN_HEIGHT - (yPadding + image.extent.height)) * 0.5 + 1
yPadding += compensateHeight
}
// Adding padding with a constant white color
let padFilter = CIFilter(name: "CICrop")!
let paddedRect = CGRect(
x: image.extent.origin.x - randomPadding[0],
y: image.extent.origin.y - randomPadding[1],
width: image.extent.width + xPadding,
height: image.extent.height + yPadding)
padFilter.setValue(image, forKey: kCIInputImageKey)
padFilter.setValue(CIVector(cgRect: paddedRect), forKey: "inputRectangle")
return padFilter.outputImage ?? image
}
// Padding images to a required size
func padding(images: [CIImage], requiredSize: CGFloat) -> [CIImage] {
return images.map { image in
let widthPadding = requiredSize - image.extent.width
let heightPadding = requiredSize - image.extent.height
return addWhiteBorder(to: image, maxSize: max(widthPadding, heightPadding))
}
}
// Transform pipeline to apply resize, normalize, etc.
func inferenceTransform(images: [NSImage]) -> [CIImage] {
let ciImages = images.compactMap { nsImageToCIImage($0) }
let trimmedImages = ciImages.compactMap { trimWhiteBorder(image: $0) }
let paddedImages = padding(images: trimmedImages, requiredSize: FIXED_IMG_SIZE)
return paddedImages
}
func ciImageToFloatArray(_ image: CIImage, size: CGSize) -> [Float] {
// Render the CIImage to a bitmap context
let context = CIContext()
guard let cgImage = context.createCGImage(image, from: image.extent) else {
return []
}
let width = Int(size.width)
let height = Int(size.height)
var pixelData = [UInt8](repeating: 0, count: width * height) // Use UInt8 for grayscale
// Create bitmap context for rendering
let colorSpace = CGColorSpaceCreateDeviceGray()
guard
let contextRef = CGContext(
data: &pixelData,
width: width,
height: height,
bitsPerComponent: 8,
bytesPerRow: width,
space: colorSpace,
bitmapInfo: CGImageAlphaInfo.none.rawValue
)
else {
return []
}
contextRef.draw(cgImage, in: CGRect(x: 0, y: 0, width: CGFloat(width), height: CGFloat(height)))
// Normalize pixel values to [0, 1]
return pixelData.map { Float($0) / 255.0 }
}
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