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Fix pixel color calculation for different data formats #28

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Fix pixel color calculation for different data formats #28

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883fa87
Add pixel color calculation using CIImage
mishpajz Sep 19, 2023
f3a8f95
Pass color space to CIContext render
mishpajz Sep 19, 2023
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45 changes: 30 additions & 15 deletions ColorKit/ColorKit/DominantColors.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -134,13 +134,28 @@ extension UIImage {
throw ImageColorError.cgImageFailure
}

let cfData = cgImage.dataProvider!.data
guard let data = CFDataGetBytePtr(cfData) else {
throw ImageColorError.cgImageDataFailure
}
// ------
// Step 2: Convert the image to RGBA8 data using CIImage
// ------

let ciImage = CIImage(cgImage: cgImage)
let imageWidth = Int(ciImage.extent.width)
let imageHeight = Int(ciImage.extent.height)

let ciContext = CIContext()
let rowBytes = 4 * imageWidth
let dataSize = rowBytes * imageHeight
var data = [UInt8](repeating: 0, count: dataSize)
ciContext.render(
ciImage,
toBitmap: &data,
rowBytes: rowBytes,
bounds: ciImage.extent,
format: .RGBA8,
colorSpace: ciImage.colorSpace)

// ------
// Step 2: Add each pixel to a NSCountedSet. This will give us a count for each color.
// Step 3: Add each pixel to a NSCountedSet. This will give us a count for each color.
// ------

let colorsCountedSet = NSCountedSet(capacity: Int(targetSize.area))
Expand All @@ -151,9 +166,9 @@ extension UIImage {
let B: UInt8
}

for yCoordonate in 0 ..< cgImage.height {
for xCoordonate in 0 ..< cgImage.width {
let index = (cgImage.width * yCoordonate + xCoordonate) * 4
for yCoordonate in 0 ..< imageHeight {
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yCoordonate should be replaced with yCoordinate, xCoordonate should be replaced with xCoordinate

for xCoordonate in 0 ..< imageWidth {
let index = (imageWidth * yCoordonate + xCoordonate) * 4

// Let's make sure there is enough alpha.
guard data[index + 3] > 150 else { continue }
Expand All @@ -164,7 +179,7 @@ extension UIImage {
}

// ------
// Step 3: Remove colors that are barely present on the image.
// Step 4: Remove colors that are barely present on the image.
// ------

let minCountThreshold = Int(targetSize.area * (0.01 / 100.0))
Expand All @@ -182,22 +197,22 @@ extension UIImage {
}

// ------
// Step 4: Sort the remaning colors by frequency.
// Step 5: Sort the remaning colors by frequency.
// ------

let sortedColorsFrequencies = filteredColorsCountMap.sorted { (lhs, rhs) -> Bool in
return lhs.frequency > rhs.frequency
}

// ------
// Step 5: Only keep the most frequent colors.
// Step 6: Only keep the most frequent colors.
// ------

let maxNumberOfColors = 500
let colorFrequencies = sortedColorsFrequencies.prefix(maxNumberOfColors)

// ------
// Step 6: Combine similar colors together.
// Step 7: Combine similar colors together.
// ------

/// The main dominant colors on the picture.
Expand Down Expand Up @@ -226,23 +241,23 @@ extension UIImage {
}

// ------
// Step 7: Again, limit the number of colors we keep, this time drastically.
// Step 8: Again, limit the number of colors we keep, this time drastically.
// ------

// We only keep the first few dominant colors.
let dominantColorsMaxCount = 8
dominantColors = Array(dominantColors.prefix(dominantColorsMaxCount))

// ------
// Step 8: Sort again on frequencies because the order may have changed because we combined colors.
// Step 9: Sort again on frequencies because the order may have changed because we combined colors.
// ------

dominantColors = dominantColors.sorted(by: { (lhs, rhs) -> Bool in
return lhs.frequency > rhs.frequency
})

// ------
// Step 9: Calculate the frequency of colors as a percentage.
// Step 10: Calculate the frequency of colors as a percentage.
// ------

/// The total count of colors
Expand Down