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Fix encoding PNG file with alpha channel on macOS #59

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Fix encoding PNG file with alpha channel on macOS #59

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31 changes: 19 additions & 12 deletions Sources/WebP/WebPEncoder+Platform.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -5,19 +5,26 @@ import AppKit
import CoreGraphics

extension WebPEncoder {
public func encode(_ image: NSImage, config: WebPEncoderConfig, width: Int = 0, height: Int = 0) throws -> Data {
guard let data = image.tiffRepresentation else {
throw WebPError.unexpectedError(withMessage: "Given image doesn't support TIFF representation.")
public func encode(_ image: NSImage,
config: WebPEncoderConfig,
width: Int = 0,
height: Int = 0) throws -> Data {
if let cgImage = image.cgImage(forProposedRect: nil,
context: nil,
hints: nil) {
let stride = cgImage.bytesPerRow
let webPData = try encode(RGBA: cgImage.getBaseAddress(),
config: config,
originWidth: Int(cgImage.width),
originHeight: Int(cgImage.height),
stride: stride,
resizeWidth: width,
resizeHeight: height)
return webPData
} else {
throw WebPError.unexpectedError(withMessage:
"Couldn't conver to CGImage")
}
guard let bitmapData = NSBitmapImageRep(data: data)?.bitmapData else {
throw WebPError.unexpectedError(withMessage: "NSBitmapImageRep couldn't interpret given image.")
}

let stride = Int(image.size.width) * MemoryLayout<UInt8>.size * 3 // RGB = 3byte
let webPData = try encode(RGB: bitmapData, config: config,
originWidth: Int(image.size.width), originHeight: Int(image.size.height), stride: stride,
resizeWidth: width, resizeHeight: height)
return webPData
}
}
#endif
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