IOS how to get the pixel value of the image

Question

I want to get the pixel value from image not color.Android has int getPixel(x, y) method,Is there a similar implementation in iOS? Note that I want to get the pixel value, not the color.

score 0 · Accepted Answer · edited May 23 '17 at 12:25

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Answer available here. The linked answer returns a UIColor object, but that is created from the RGB data that is read, so it is available.

You can modify that answer to match Android's documentation:

The components are stored as follows (alpha << 24) | (red << 16) | (green << 8) | blue

red = rawData[byteIndex];
green = rawData[byteIndex + 1];
blue = rawData[byteIndex + 2];
alpha = rawData[byteIndex + 3];

NSInteger pixel = (alpha << 24) | (red << 16) | (green << 8) | blue; // 32 or 64bits depending on device
int32_t androidPixel = (int32_t)pixel; // Guaranteed 32 bits like android/java `int`

Note that although android's documentation implies this is an int, a color such as opaque black looks like 0xFF000000, meaning it will appear as a negative number in a 32 bit int. Using an unsigned integer or 64 bit integer will appear to have a different result although the bits are the same.

edited May 23 '17 at 12:25

Community

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answered Feb 20 '17 at 03:38

arsenius

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I don't want RGB,I want a pixel value,like Android's `int getPixel(x, y)` method. `get Pixel(x, y)` method return a int value, not RGB. – 发抖喵小咪 Feb 20 '17 at 03:45
@发抖喵小咪 That "int value" is an int encoding 4 byte components (ARGB) – Alexander Feb 20 '17 at 04:00
i got a positive integer through this method,but android's `int getPixel(x, y)` method get a negtive integer. then what can i do? – 发抖喵小咪 Feb 20 '17 at 05:37
all values of android is negtive integer. – 发抖喵小咪 Feb 20 '17 at 05:38

score 0 · Answer 2 · answered Feb 20 '17 at 17:28

Getting pixel size is simple task. There two ways you can get image pixel size. Try one of the following method.

Using cgImage

let image = UIImage(named: "test")
let width = image?.cgImage.width // Pixel width
let height = image?.cgImage.height // Pixel height
let imageSize = CGSize(width: width, height: height) //Image Pixel Size
print("Image Pixel Size: \(imageSize)")

Using PNG Data

let image = UIImage(named: "test")
let imageData: Data = UIImagePNGRepresentation(image)! // Get PNG Image Data
let image: UIImage = UIImage(data: imageData)!  // Get image from PNG Data
let  imageSize = image.size // Finally get size from png Image
print("Image Pixel Size: \(imageSize)")

Your answer is not what I want. – 发抖喵小咪 Feb 21 '17 at 01:26 — 发抖喵小咪, Feb 21 '17 at 01:26

IOS how to get the pixel value of the image

2 Answers2