Wie dekodiere ich die COCO RLE-Binärmaske in ein Bild in JavaScript?

Question

Dies ist ein Beispiel einer COCO RLE-Maske – https://pastebin.com/ZhE2en4C

Dies ist die Ausgabe des YOLOv8-Validierungslaufs, entnommen aus der generierten Predictions.json-Datei.

Ich versuche, diese Zeichenfolge in JavaScript zu dekodieren und auf der Leinwand darzustellen. Die codierte Zeichenfolge ist gültig, da ich in Python Folgendes tun kann:

from pycocotools import mask as coco_mask
from PIL import Image

example_prediction = {
    "image_id": "102_jpg",
    "category_id": 0,
    "bbox": [153.106, 281.433, 302.518, 130.737],
    "score": 0.8483,
    "segmentation": {
      "size": [640, 640],
      "counts": "<RLE string here>"
    }
  }

def rle_to_bitmap(rle):
  bitmap = coco_mask.decode(rle)
  return bitmap

def show_bitmap(bitmap):
  img = Image.fromarray(bitmap.astype(np.uint8) * 255, mode='L')
  img.show()
  input("Press Enter to continue...")
  img.close()
    

mask_bitmap = rle_to_bitmap(example_prediction["segmentation"])
show_bitmap(mask_bitmap)

Ich kann die entschlüsselte Maske sehen.

Gibt es eine Bibliothek, die verwendet werden kann, um dieselbe Zeichenfolge in JavaScript zu dekodieren und in Image zu konvertieren? Ich habe versucht, in den Quellcode von Pycocotools einzutauchen, aber es gelang mir nicht.

Answer 1

您可以在画布上绘制蒙版，然后根据需要导出图像。

对于实际绘图，您可以使用两种方法：

1. 将 RLE 解码为二进制掩码（二维矩阵或展平矩阵），然后根据该掩码绘制像素
2. 直接从虚拟画布上的 RLE 字符串绘制蒙版，然后将其旋转 90 度并水平翻转

以下是两者的示例：

// Styling and scaling just for demo
let wrapper = document.createElement("div")
wrapper.style.cssText = `
  transform-origin: left top;
  transform: scale(8);
`
document.body.style.cssText = `
  background-color: #121212;
  margin: 0;
  overflow: hidden;
`
document.body.appendChild(wrapper)

// Helpers
function createCanvas(width, height) {
  let canvas = document.createElement("canvas")

  canvas.style.cssText = `
    border: 1px solid white;
    display: block;
    float: left;
    image-rendering: pixelated;
  `
  canvas.height = height
  canvas.width = width

  // Comment this line if you need only image sources
  wrapper.appendChild(canvas)

  return canvas
}

function randomColorRGBA() {
  return [
        Math.round(Math.random() * 255),
        Math.round(Math.random() * 255),
        Math.round(Math.random() * 255),
        255
      ]
}

// Fast array flattening (faster than Array.proto.flat())
function flatten(arr) {
  const flattened = []

  !(function flat(arr) {
    arr.forEach((el) => {
      if (Array.isArray(el)) flat(el)
      else flattened.push(el)
    })
  })(arr)

  return flattened
}

// Decode from RLE to Binary Mask
// (pass false to flat argument if you need 2d matrix output)
function decodeCocoRLE([rows, cols], counts, flat = true) {
  let pixelPosition = 0,
      binaryMask
  
  if (flat) {
    binaryMask = Array(rows * cols).fill(0)
  } else {
    binaryMask = Array.from({length: rows}, (_) => Array(cols).fill(0))
  }

  for (let i = 0, rleLength = counts.length; i  0) {
      const rowIndex = pixelPosition % rows,
            colIndex = (pixelPosition - rowIndex) / rows

      if (flat) {
        const arrayIndex = rowIndex * cols + colIndex
        binaryMask[arrayIndex] = 1
      } else {
        binaryMask[rowIndex][colIndex] = 1
      }

      pixelPosition++
      ones--
    }
  }

  if (!flat) {
    console.log("Result matrix:")
    binaryMask.forEach((row, i) => console.log(row.join(" "), `- row ${i}`))
  }

  return binaryMask
}

// 1. Draw from binary mask
function drawFromBinaryMask({size, counts}) {
  let fillColor = randomColorRGBA(),
      height = size[0],
      width = size[1]

  let canvas = createCanvas(width, height),
      canvasCtx = canvas.getContext("2d"),
      imgData = canvasCtx.getImageData(0, 0, width, height),
      pixelData = imgData.data

  // If you need matrix output (flat = false)
  // let maskFlattened = flatten(decodeCocoRLE(size, counts, false)),
  //     maskLength = maskFlattened.length;
  
  // If not - it's better to use faster approach
  let maskFlattened = decodeCocoRLE(size, counts),
      maskLength = maskFlattened.length;

  for(let i = 0; i  {
    end = start + interval * 4
    if (isOnesInterval) {
      for (let i = start; i  {
  wrapper.appendChild(image1)
}
image2.onload = () => {
  wrapper.appendChild(image2)
}

image1.src = imageSrc1
image2.src = imageSrc2