I have a UIImage which comes from ARKit. I want to be able to sample the color of this image with high precision. Search for sample color of UIImage or CGImage returns code like below, which gives me four UInt8 components.
I tried altering the bits per component, but don't know how to adjust other parameters of CGContext to make it render.
How do I specify that CoreGraphics render UIImage using 16 bit color components? (Or something other than UInt8?)
let result = renderer.image { imageRendererContext in
let context = imageRendererContext.cgContext
context.setStrokeColor(UIColor.clear.cgColor)
let maskWidth = Int(mask.size.width)
let maskHeight = Int(mask.size.height)
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bytesPerPixel = 4
let bytesPerRow = bytesPerPixel * maskWidth
let bitsPerComponent = 8
let bitmapInfo: UInt32 = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Big.rawValue
guard let maskContext = CGContext(data: nil,
width: maskWidth,
height: maskHeight,
bitsPerComponent: bitsPerComponent,
bytesPerRow: bytesPerRow,
space: colorSpace,
bitmapInfo: bitmapInfo),
let maskPointer = maskContext.data?.assumingMemoryBound(to: UInt8.self) else {
return
}
maskContext.draw(maskCGImage, in: CGRect(x: 0, y: 0, width: maskWidth, height: maskHeight))
for x in 0 ..< maskWidth {
for y in 0 ..< maskHeight {
let i = bytesPerRow * Int(y) + bytesPerPixel * Int(x)
let a = CGFloat(maskPointer[i + 3]) / 255.0
let r = (CGFloat(maskPointer[i]) / a) / 255.0
let g = (CGFloat(maskPointer[i + 1]) / a) / 255.0
let b = (CGFloat(maskPointer[i + 2]) / a) / 255.0
}
}
}
Found that as described in the core graphics guide, 16 bits per component and higher is only available on MacOS, not iOS
Related
I'm trying to implement batching for a WebGL renderer which is struggling with lots of small objects due to too many draw calls. What I thought is I'd batch them all by the kind of shader they use, then draw a few at a time, uploading material parameters and the model matrix for each object once in uniforms.
My problem is that the uniform size limits for non-UBO uniforms are extremely low, as in 256 floats low at a minimum. If my material uses, say, 8 floats, and if you factor in the model matrix, I barely have enough uniforms to draw 10 models in a single batch, which isn't really going to be enough.
Is there any hope to make this work without UBOs? Are textures an option? How are people doing batching without WebGL2 UBOs?
More details: I have no skinning or complex animations, I just have some shaders (diffuse, cook-torrance, whatever) and each model has different material settings for each shader, e.g. color, roughness, index of refraction which can be changed dynamically by the user (so it's not realistic to bake them into the vertex array because we have some high poly data, also users can switch shaders and not all shaders have the same number of parameters) as well as material maps obviously. The geometry itself is static and just has a linear transform on each model. For the most part all meshes are different so geometry instancing won't help a whole lot, but I can look at that later.
Thanks
I don't know that this is actually faster than lots of draw calls but here is drawing 4 models with a single draw call
It works by adding an id per model. So, for every vertex in model #0 put a 0, for every vertex in model #1 put a 1, etc.
Then it uses model id to index stuff in a texture. The easiest would be model id chooses the row of a texture and then all the data for that model can be pulled out of that row.
For WebGL1
attribute float modelId;
...
#define TEXTURE_WIDTH ??
#define COLOR_OFFSET ((0.0 + 0.5) / TEXTURE_WIDTH)
#define MATERIAL_OFFSET ((1.0 + 0.5) / TEXTURE_WIDTH)
float modelOffset = (modelId + .5) / textureHeight;
vec4 color = texture2D(perModelData, vec2(COLOR_OFFSET, modelOffset));
vec4 roughnessIndexOfRefaction = texture2D(perModelData,
vec2(MATERIAL_OFFSET, modelOffset));
etc..
As long as you are not drawing more than gl.getParameter(gl.MAX_TEXTURE_SIZE) models it will work. If you have more than that either use more draw calls or change the texture coordinate calculations so there's more than one model per row
In WebGL2 you'd change the code to use texelFetch and unsigned integers
in uint modelId;
...
#define COLOR_OFFSET 0
#define MATERIAL_OFFSET 1
vec4 color = texelFetch(perModelData, uvec2(COLOR_OFFSET, modelId));
vec4 roughnessIndexOfRefaction = texelFetch(perModelData,
uvec2(MATERIAL_OFFSET, modelId));
example of 4 models drawn with 1 draw call. For each model the model matrix and color are stored in the texture.
const m4 = twgl.m4;
const v3 = twgl.v3;
const gl = document.querySelector('canvas').getContext('webgl');
const ext = gl.getExtension('OES_texture_float');
if (!ext) {
alert('need OES_texture_float');
}
const COMMON_STUFF = `
#define TEXTURE_WIDTH 5.0
#define MATRIX_ROW_0_OFFSET ((0. + 0.5) / TEXTURE_WIDTH)
#define MATRIX_ROW_1_OFFSET ((1. + 0.5) / TEXTURE_WIDTH)
#define MATRIX_ROW_2_OFFSET ((2. + 0.5) / TEXTURE_WIDTH)
#define MATRIX_ROW_3_OFFSET ((3. + 0.5) / TEXTURE_WIDTH)
#define COLOR_OFFSET ((4. + 0.5) / TEXTURE_WIDTH)
`;
const vs = `
attribute vec4 position;
attribute vec3 normal;
attribute float modelId;
uniform float textureHeight;
uniform sampler2D perModelDataTexture;
uniform mat4 projection;
uniform mat4 view;
varying vec3 v_normal;
varying float v_modelId;
${COMMON_STUFF}
void main() {
v_modelId = modelId; // pass to fragment shader
float modelOffset = (modelId + 0.5) / textureHeight;
// note: in WebGL2 better to use texelFetch
mat4 model = mat4(
texture2D(perModelDataTexture, vec2(MATRIX_ROW_0_OFFSET, modelOffset)),
texture2D(perModelDataTexture, vec2(MATRIX_ROW_1_OFFSET, modelOffset)),
texture2D(perModelDataTexture, vec2(MATRIX_ROW_2_OFFSET, modelOffset)),
texture2D(perModelDataTexture, vec2(MATRIX_ROW_3_OFFSET, modelOffset)));
gl_Position = projection * view * model * position;
v_normal = mat3(view) * mat3(model) * normal;
}
`;
const fs = `
precision highp float;
varying vec3 v_normal;
varying float v_modelId;
uniform float textureHeight;
uniform sampler2D perModelDataTexture;
uniform vec3 lightDirection;
${COMMON_STUFF}
void main() {
float modelOffset = (v_modelId + 0.5) / textureHeight;
vec4 color = texture2D(perModelDataTexture, vec2(COLOR_OFFSET, modelOffset));
float l = dot(lightDirection, normalize(v_normal)) * .5 + .5;
gl_FragColor = vec4(color.rgb * l, color.a);
}
`;
// compile shader, link, look up locations
const programInfo = twgl.createProgramInfo(gl, [vs, fs]);
// make some vertex data
const modelVerts = [
twgl.primitives.createSphereVertices(1, 6, 4),
twgl.primitives.createCubeVertices(1, 1, 1),
twgl.primitives.createCylinderVertices(1, 1, 10, 1),
twgl.primitives.createTorusVertices(1, .2, 16, 8),
];
// merge all the vertices into one
const arrays = twgl.primitives.concatVertices(modelVerts);
// fill an array so each vertex of each model has a modelId
const modelIds = new Uint16Array(arrays.position.length / 3);
let offset = 0;
modelVerts.forEach((verts, modelId) => {
const end = offset + verts.position.length / 3;
while(offset < end) {
modelIds[offset++] = modelId;
}
});
arrays.modelId = { numComponents: 1, data: modelIds };
// calls gl.createBuffer, gl.bindBuffer, gl.bufferData
const bufferInfo = twgl.createBufferInfoFromArrays(gl, arrays);
const numModels = modelVerts.length;
const tex = gl.createTexture();
const textureWidth = 5; // 4x4 matrix, 4x1 color
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, textureWidth, numModels, 0, gl.RGBA, gl.FLOAT, null);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
// this data is for the texture, one row per model
// first 4 pixels are the model matrix, 5 pixel is the color
const perModelData = new Float32Array(textureWidth * numModels * 4);
const stride = textureWidth * 4;
const modelOffset = 0;
const colorOffset = 16;
// set the colors at init time
for (let modelId = 0; modelId < numModels; ++modelId) {
perModelData.set([r(), r(), r(), 1], modelId * stride + colorOffset);
}
function r() {
return Math.random();
}
function render(time) {
time *= 0.001; // seconds
twgl.resizeCanvasToDisplaySize(gl.canvas);
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
gl.enable(gl.DEPTH_TEST);
gl.enable(gl.CULL_FACE);
const fov = Math.PI * 0.25;
const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
const near = 0.1;
const far = 20;
const projection = m4.perspective(fov, aspect, near, far);
const eye = [0, 0, 10];
const target = [0, 0, 0];
const up = [0, 1, 0];
const camera = m4.lookAt(eye, target, up);
const view = m4.inverse(camera);
// set the matrix for each model in the texture data
const mat = m4.identity();
for (let modelId = 0; modelId < numModels; ++modelId) {
const t = time * (modelId + 1) * 0.3;
m4.identity(mat);
m4.rotateX(mat, t, mat);
m4.rotateY(mat, t, mat);
m4.translate(mat, [0, 0, Math.sin(t * 1.1) * 4], mat);
m4.rotateZ(mat, t, mat);
perModelData.set(mat, modelId * stride + modelOffset);
}
// upload the texture data
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, 0, textureWidth, numModels,
gl.RGBA, gl.FLOAT, perModelData);
gl.useProgram(programInfo.program);
// calls gl.bindBuffer, gl.enableVertexAttribArray, gl.vertexAttribPointer
twgl.setBuffersAndAttributes(gl, programInfo, bufferInfo);
// calls gl.activeTexture, gl.bindTexture, gl.uniformXXX
twgl.setUniforms(programInfo, {
lightDirection: v3.normalize([1, 2, 3]),
perModelDataTexture: tex,
textureHeight: numModels,
projection,
view,
});
// calls gl.drawArrays or gl.drawElements
twgl.drawBufferInfo(gl, bufferInfo);
requestAnimationFrame(render);
}
requestAnimationFrame(render);
body { margin: 0; }
canvas { width: 100vw; height: 100vh; display: block; }
<script src="https://twgljs.org/dist/4.x/twgl-full.min.js"></script>
<canvas></canvas>
Here's 2000 models in one draw call
https://jsfiddle.net/greggman/g2tcadho/
I'm trying to set a SKLabelNode's position to the center of a SKSpriteNode.
I've looked at other questions on this but none of these work with Swift 3.
This is my code:
var letter1background = SKSpriteNode(imageNamed: "letterbackground")
var letter1text = SKLabelNode()
override func didMove(to view: SKView) {
letter1background.position = CGPoint(x: self.size.width / 8, y: self.size.height / 7.5)
letter1background.size = CGSize(width: self.size.width / 8, height: self.size.width / 8)
letter1background.zPosition = -5
self.addChild(letter1background)
letter1text.text = "C"
letter1text.fontName = "Verdana-Bold "
letter1text.fontSize = 28
letter1text.fontColor = UIColor.white
letter1text.zPosition = 0
letter1text.horizontalAlignmentMode = letter1background.center
letter1text.verticalAlignmentMode = letter1background.center
self.letter1background.addChild(letter1text)
}
This code looks like it would work but in Swift 3 I now get this error:
Value of type 'SKSpriteNode' has no member 'center'
I have also tried:
self.letter1text.position = CGPoint(x: letter1background.frame.width/2 - (letter1text.frame.width/2), y: letter1background.frame.height/2 -(letter1text.frame.height/2))
&
letter1text.position = CGPoint(x:letter1background.frame.midX, y:letter1background.frame.midY)
But I still get results like this:
Any ideas?
Your calculations of label's position are wrong. You just have to add a label to the at 0,0 position and it will be centered because of SpriteKit's coordinate system rules (0,0 is at the center of the node).
override func didMove(to view: SKView) {
let label = SKLabelNode(fontNamed: "Arial")
label.text = "C"
label.fontColor = .black
label.verticalAlignmentMode = .center
label.fontSize = 29.0
label.zPosition = 1
let background = SKSpriteNode(color: .green, size: CGSize(width: 50, height: 50))
background.addChild(label)
addChild(background)
}
And you will get this:
I want to translate this line to the Swift 3 current syntax code but seems there are some problems:
CGContextDrawImage(context, CGRect(x:0.0,y: 0.0,width: image!.size.width,height: image!.size.height), image!.cgImage)
According to the CoreGraphics.apinotes CGContextDrawImage was converted to CGContext.draw :
Name: CGContextDrawImage
# replaced by draw(_ image: CGImage, in rect: CGRect, byTiling: Bool = false)
SwiftName: CGContext.__draw(self:in:image:)
SwiftPrivate: true
When I try to do :
CGContext.draw(context as! CGImage, in: CGRect(x:0.0, y:0.0, width: image!.size.width, height: image!.size.height), byTiling: false)
Seems there is some simple syntax that disturb the compiler but I cannot see (in fact I receive a typical ambiguous error):
Can anyone help me with this new swift 3 syntax code?
You need to call it as if it's an instance method of CGContext:
context.draw(image!.cgImage!, in: CGRect(x: 0.0,y: 0.0,width: image!.size.width,height: image!.size.height))
Check the latest reference of CGContext.
I have found an another very good solution for this issue which i am using currently. You just need to pass the image as an arugument to this method after capturing image using UIImagePickerController. It works well for all version of iOS and also for both portrait and landscape orientations of Camera. It checks for EXIF property of image using UIImageOrientaiton and accordind to the value of orientation, it transforms & scales the image so you will get the same return image with same orientation as your camera view orientation.
Here i have kept maximum resolutions of 3000 so that the image quality doesn't get spoiled specially while you are using retina devices but you can change its resolution as per your requirement.
func scaleAndRotateImage(image: UIImage, MaxResolution iIntMaxResolution: Int) -> UIImage {
let kMaxResolution = iIntMaxResolution
let imgRef = image.cgImage!
let width: CGFloat = CGFloat(imgRef.width)
let height: CGFloat = CGFloat(imgRef.height)
var transform = CGAffineTransform.identity
var bounds = CGRect.init(x: 0, y: 0, width: width, height: height)
if Int(width) > kMaxResolution || Int(height) > kMaxResolution {
let ratio: CGFloat = width / height
if ratio > 1 {
bounds.size.width = CGFloat(kMaxResolution)
bounds.size.height = bounds.size.width / ratio
}
else {
bounds.size.height = CGFloat(kMaxResolution)
bounds.size.width = bounds.size.height * ratio
}
}
let scaleRatio: CGFloat = bounds.size.width / width
let imageSize = CGSize.init(width: CGFloat(imgRef.width), height: CGFloat(imgRef.height))
var boundHeight: CGFloat
let orient = image.imageOrientation
// The output below is limited by 1 KB.
// Please Sign Up (Free!) to remove this limitation.
switch orient {
case .up:
//EXIF = 1
transform = CGAffineTransform.identity
case .upMirrored:
//EXIF = 2
transform = CGAffineTransform.init(translationX: imageSize.width, y: 0.0)
transform = transform.scaledBy(x: -1.0, y: 1.0)
case .down:
//EXIF = 3
transform = CGAffineTransform.init(translationX: imageSize.width, y: imageSize.height)
transform = transform.rotated(by: CGFloat(Double.pi / 2))
case .downMirrored:
//EXIF = 4
transform = CGAffineTransform.init(translationX: 0.0, y: imageSize.height)
transform = transform.scaledBy(x: 1.0, y: -1.0)
case .leftMirrored:
//EXIF = 5
boundHeight = bounds.size.height
bounds.size.height = bounds.size.width
bounds.size.width = boundHeight
transform = CGAffineTransform.init(translationX: imageSize.height, y: imageSize.width)
transform = transform.scaledBy(x: -1.0, y: 1.0)
transform = transform.rotated(by: CGFloat(Double.pi / 2) / 2.0)
break
default: print("Error in processing image")
}
UIGraphicsBeginImageContext(bounds.size)
let context = UIGraphicsGetCurrentContext()
if orient == .right || orient == .left {
context?.scaleBy(x: -scaleRatio, y: scaleRatio)
context?.translateBy(x: -height, y: 0)
}
else {
context?.scaleBy(x: scaleRatio, y: -scaleRatio)
context?.translateBy(x: 0, y: -height)
}
context?.concatenate(transform)
context?.draw(imgRef, in: CGRect.init(x: 0, y: 0, width: width, height: height))
let imageCopy = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return imageCopy!
}
How can I plot an array to an imageview as a graph?
I've been testing this in Playground and it works, but how can plot this as an imageview in an actual project?
let sineArraySize = 64
let frequency1 = 4.0
let phase1 = 0.0
let amplitude1 = 2.0
let sineWave = (0..<sineArraySize).map {
amplitude1 * sin(2.0 * M_PI / Double(sineArraySize) * Double($0) * frequency1 + phase1)
}
func plotArrayInPlayground<T>(arrayToPlot:Array<T>, title:String) {
for currentValue in arrayToPlot {
XCPCaptureValue(title, currentValue)
}
}
plotArrayInPlayground(sineWave, "Sine wave 1")
One way you could do this:
// this function creates a plot of an array of doubles where it scales to the provided width and the x-axis is on half height
func plotArray(arr: [Double], width: Double, height: Double) -> NSImage {
if arr.isEmpty { return NSImage() }
let xAxisHeight = height / 2
let increment = width / Double(arr.count)
let image = NSImage(size: NSSize(width: width, height: height))
image.lockFocus()
// set background color
NSColor.whiteColor().set()
NSRectFill(NSRect(x: 0, y: 0, width: width, height: height))
let path = NSBezierPath()
// line width of plot
path.lineWidth = 5
path.moveToPoint(NSPoint(x: 0, y: arr[0] * increment + xAxisHeight))
var i = increment
for value in dropFirst(sineWave) {
path.lineToPoint(NSPoint(x: i, y: value * increment + xAxisHeight))
i += increment
}
// set plot color
NSColor.blueColor().set()
path.stroke()
image.unlockFocus()
return image
}
var imageView = NSImageView()
imageView.image = plotArray(sineWave, 500, 200)
// have fun
Is there a way I can change the color space of an NSimage or NSBitmapImageRep/CGimage or the like. I am open to any way. Preferably the way photoshop does it.
The problem with the code you see below
CGImageRef CGImageCreateCopyWithColorSpace (
CGImageRef image,
CGColorSpaceRef colorspace
);
is not working because Quartz2D does not support alpha for CMYK images or gray images, it is supported only by RGB images.
What you should do is creating 2 images then combine then in case of a CMYK color space and image with alpha. I have searched a lot about this topic and finally found. May be author of this question doesn't need it anymore but someone else may need it.
Create new NSBitmapImageRep
let imageRep = NSBitmapImageRep(bitmapDataPlanes: nil,
pixelsWide: Int(round(imageSize.width)),
pixelsHigh: Int(round(imageSize.height)),
bitsPerSample: 8,
samplesPerPixel: 4,
hasAlpha: false,
isPlanar: false,
colorSpaceName: NSDeviceCMYKColorSpace,
bitmapFormat: NSBitmapFormat(rawValue: 0),
bytesPerRow: Int(round(imageSize.width) * CGFloat(4)),
bitsPerPixel: 0)
You need to draw your image into the new bitmap
lets say you have colorSpace: NSColorSpace
let context = NSGraphicsContext(bitmapImageRep: imageRep)
NSGraphicsContext.saveGraphicsState()
NSGraphicsContext.setCurrentContext(context)
imageRep.setProperty(NSImageColorSyncProfileData, withValue: colorSpace.ICCProfileData)
// Do your drawing here
NSGraphicsContext.restoreGraphicsState()
After this you will have an imageRep that is the image with correct color space but no alpha (transparency).
You need a mask bitmap. Obtaining mask is tricky.
let imageRep = NSBitmapImageRep(bitmapDataPlanes: nil,
pixelsWide: Int(round(imageSize.width)),
pixelsHigh: Int(round(imageSize.height)),
bitsPerSample: 8,
samplesPerPixel: 1,
hasAlpha: false,
isPlanar: false,
colorSpaceName: NSDeviceWhiteColorSpace,
bitmapFormat: NSBitmapFormat(rawValue: 0),
bytesPerRow: Int(round(imageSize.width)),
bitsPerPixel: 0)
Clip white image to your image with transparency
if let graphicsPort = NSGraphicsContext.currentContext()?.graphicsPort {
let context = unsafeBitCast(graphicsPort, CGContextRef.self)
let imgRect = NSRect(origin: NSPoint.zero, size: image.extent.size)
let ciContext = CIContext()
let cgImage = ciContext.createCGImage(image, fromRect: image.extent)
CGContextClipToMask(context, imgRect, cgImage)
}
Colorize all pixel in white color, this will be clipped to image.
let context = NSGraphicsContext(bitmapImageRep: imageRep)
NSGraphicsContext.saveGraphicsState()
NSGraphicsContext.setCurrentContext(context)
imageRep.setProperty(NSImageColorSyncProfileData, withValue: colorSpace.ICCProfileData)
NSColor.whiteColor().setFill()
NSBezierPath.fillRect(NSRect(origin: NSPoint.zero, size: imageSize))
NSGraphicsContext.restoreGraphicsState()
At this step you have a image and a mask. Next we need to combine them. I am using this little algorithm (you need to verify that mask and source image have same sizes and same colorSpaceModel):
func createCMYKAImageRepByApplingAlphaMask(srcImageRep: NSBitmapImageRep, alphaMaskImageRep alphaMask: NSBitmapImageRep) -> NSBitmapImageRep? {
if canApplyMaskRepOnImageRep(srcImageRep, maskRep: alphaMask) == false {
return nil
}
let alphaData = alphaMask.bitmapData
let srcData = srcImageRep.bitmapData
if let imageWithAlphaMaskRep = createEmptyCMYKABitmapImageRep(alphaMask.size) {
if let colorSpaceData = imageColorSpace?.ICCProfileData {
imageWithAlphaMaskRep.setProperty(NSImageColorSyncProfileData, withValue: colorSpaceData)
}
fillPixelsWithComponentsData(imageWithAlphaMaskRep, components: { (pixelIdx: Int) -> (UInt8, UInt8, UInt8, UInt8, UInt8) in
let cyan = srcData[pixelIdx * 4 + 0]
let magenta = srcData[pixelIdx * 4 + 1]
let yellow = srcData[pixelIdx * 4 + 2]
let black = srcData[pixelIdx * 4 + 3]
let alpha = alphaData[pixelIdx]
return (cyan, magenta, yellow, black, alpha)
})
return imageWithAlphaMaskRep
}
return nil
}
func createEmptyBitmapImageRep() -> NSBitmapImageRep? {
let imageRep = NSBitmapImageRep(bitmapDataPlanes: nil,
pixelsWide: Int(round(imageSize.width)),
pixelsHigh: Int(round(imageSize.height)),
bitsPerSample: 8,
samplesPerPixel: 5,
hasAlpha: true,
isPlanar: false,
colorSpaceName: NSDeviceCMYKColorSpace,
bitmapFormat: NSBitmapFormat(rawValue: 0),
bytesPerRow: Int(round(imageSize.width) * CGFloat(5)),
bitsPerPixel: 0)
return imageRep
}
private func fillPixelsWithComponentsData(imgRep: NSBitmapImageRep,
components: (Int) -> (cyan:UInt8, magenta:UInt8, yellow:UInt8, black:UInt8, alpha:UInt8)) {
let imageRawData = imgRep.bitmapData
let imageWidth = Int(imgRep.size.width)
let imageHeight = Int(imgRep.size.height)
for pixelIdx in 0 ..< (imageWidth * imageHeight) {
let (cyan, magenta, yellow, black, alpha) = components(pixelIdx)
let fAlpha = Float(alpha) / 255
imageRawData[pixelIdx * 5 + 0] = UInt8(Float(cyan) * fAlpha)
imageRawData[pixelIdx * 5 + 1] = UInt8(Float(magenta) * fAlpha)
imageRawData[pixelIdx * 5 + 2] = UInt8(Float(yellow) * fAlpha)
imageRawData[pixelIdx * 5 + 3] = UInt8(Float(black) * fAlpha)
imageRawData[pixelIdx * 5 + 4] = alpha
}
}
CGImageRef CGImageCreateCopyWithColorSpace (
CGImageRef image,
CGColorSpaceRef colorspace
);
To get a CGColorSpaceRef, you can do things like
CGColorSpaceRef CGColorSpaceCreateDeviceRGB();
OR see this page for how to create other color spaces.