我有一个UIImage (Cocoa Touch)。从那里，我很高兴得到一个CGImage或任何你想要的可用的东西。我想写这个函数:
- (int)getRGBAFromImage:(UIImage *)image atX:(int)xx andY:(int)yy {
// [...]
// What do I want to read about to help
// me fill in this bit, here?
// [...]
int result = (red << 24) | (green << 16) | (blue << 8) | alpha;
return result;
}
当前回答
基于Olie和Algal的回答，以下是Swift 3的最新答案
public func getRGBAs(fromImage image: UIImage, x: Int, y: Int, count: Int) -> [UIColor] {
var result = [UIColor]()
// First get the image into your data buffer
guard let cgImage = image.cgImage else {
print("CGContext creation failed")
return []
}
let width = cgImage.width
let height = cgImage.height
let colorSpace = CGColorSpaceCreateDeviceRGB()
let rawdata = calloc(height*width*4, MemoryLayout<CUnsignedChar>.size)
let bytesPerPixel = 4
let bytesPerRow = bytesPerPixel * width
let bitsPerComponent = 8
let bitmapInfo: UInt32 = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Big.rawValue
guard let context = CGContext(data: rawdata, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo) else {
print("CGContext creation failed")
return result
}
context.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))
// Now your rawData contains the image data in the RGBA8888 pixel format.
var byteIndex = bytesPerRow * y + bytesPerPixel * x
for _ in 0..<count {
let alpha = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 3, as: UInt8.self)) / 255.0
let red = CGFloat(rawdata!.load(fromByteOffset: byteIndex, as: UInt8.self)) / alpha
let green = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 1, as: UInt8.self)) / alpha
let blue = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 2, as: UInt8.self)) / alpha
byteIndex += bytesPerPixel
let aColor = UIColor(red: red, green: green, blue: blue, alpha: alpha)
result.append(aColor)
}
free(rawdata)
return result
}
斯威夫特
其他回答
NSString * path = [[NSBundle mainBundle] pathForResource:@"filename" ofType:@"jpg"];
UIImage * img = [[UIImage alloc]initWithContentsOfFile:path];
CGImageRef image = [img CGImage];
CFDataRef data = CGDataProviderCopyData(CGImageGetDataProvider(image));
const unsigned char * buffer = CFDataGetBytePtr(data);
基于Olie和Algal的回答，以下是Swift 3的最新答案
public func getRGBAs(fromImage image: UIImage, x: Int, y: Int, count: Int) -> [UIColor] {
var result = [UIColor]()
// First get the image into your data buffer
guard let cgImage = image.cgImage else {
print("CGContext creation failed")
return []
}
let width = cgImage.width
let height = cgImage.height
let colorSpace = CGColorSpaceCreateDeviceRGB()
let rawdata = calloc(height*width*4, MemoryLayout<CUnsignedChar>.size)
let bytesPerPixel = 4
let bytesPerRow = bytesPerPixel * width
let bitsPerComponent = 8
let bitmapInfo: UInt32 = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Big.rawValue
guard let context = CGContext(data: rawdata, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo) else {
print("CGContext creation failed")
return result
}
context.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))
// Now your rawData contains the image data in the RGBA8888 pixel format.
var byteIndex = bytesPerRow * y + bytesPerPixel * x
for _ in 0..<count {
let alpha = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 3, as: UInt8.self)) / 255.0
let red = CGFloat(rawdata!.load(fromByteOffset: byteIndex, as: UInt8.self)) / alpha
let green = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 1, as: UInt8.self)) / alpha
let blue = CGFloat(rawdata!.load(fromByteOffset: byteIndex + 2, as: UInt8.self)) / alpha
byteIndex += bytesPerPixel
let aColor = UIColor(red: red, green: green, blue: blue, alpha: alpha)
result.append(aColor)
}
free(rawdata)
return result
}
斯威夫特
这是一个SO线程，其中@Matt通过替换图像只渲染所需的像素到1x1上下文，以便所需的像素与上下文中的一个像素对齐。
根据不同的答案，但主要是在这一点上，这是我需要的:
UIImage *image1 = ...; // The image from where you want a pixel data
int pixelX = ...; // The X coordinate of the pixel you want to retrieve
int pixelY = ...; // The Y coordinate of the pixel you want to retrieve
uint32_t pixel1; // Where the pixel data is to be stored
CGContextRef context1 = CGBitmapContextCreate(&pixel1, 1, 1, 8, 4, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaNoneSkipFirst);
CGContextDrawImage(context1, CGRectMake(-pixelX, -pixelY, CGImageGetWidth(image1.CGImage), CGImageGetHeight(image1.CGImage)), image1.CGImage);
CGContextRelease(context1);
由于这些行，您将拥有一个AARRGGBB格式的像素，alpha总是设置为FF，在4字节无符号整数pixel1中。
要在Swift 5中访问UIImage的原始RGB值，请使用底层CGImage及其dataProvider:
import UIKit
let image = UIImage(named: "example.png")!
guard let cgImage = image.cgImage,
let data = cgImage.dataProvider?.data,
let bytes = CFDataGetBytePtr(data) else {
fatalError("Couldn't access image data")
}
assert(cgImage.colorSpace?.model == .rgb)
let bytesPerPixel = cgImage.bitsPerPixel / cgImage.bitsPerComponent
for y in 0 ..< cgImage.height {
for x in 0 ..< cgImage.width {
let offset = (y * cgImage.bytesPerRow) + (x * bytesPerPixel)
let components = (r: bytes[offset], g: bytes[offset + 1], b: bytes[offset + 2])
print("[x:\(x), y:\(y)] \(components)")
}
print("---")
}
https://www.ralfebert.de/ios/examples/image-processing/uiimage-raw-pixels/
