Conversion between compoundPath and coco segmentation

[JinDing123]

Hello, may I ask if the compoundPath function in paper.js can be used to achieve the conversion between coco segmentation and compoundPath? I need to convert a compoundPath into segmentation, and at the same time, I also need to convert segmentation into compoundPath, all based on the image's width and height. I hope there is such a similar function.

`
function compoundPathJsonToSegmentation(
compoundPathJson,
imageWidth,
imageHeight,

) {}

function segmentationToCompoundPathJson(
segmentation,
imageWidth,
imageHeight,
) {}
`

this is the example data of compoundPath and segmentation
`
;[
'CompoundPath',
{
applyMatrix: true,
opacity: 0.6,
data: {
annotationId: 0,
categoryId: 0,
uuid: 'aec8b72c-8b7d-450e-a69b-7103deed0615',
},
children: [
[
'Path',
{
applyMatrix: true,
segments: [
[-139, -346],
[-122, -344],
[-62, -345],
[-17, -343],
[5, -340],
[16, -336],
[20, -336],
[28, -333],
[32, -329],
[33, -320],
[30, -305],
[25, -293],
[25, -287],
[23, -282],
[15, -274],
[15, -269],
[18, -263],
[17, -250],
[9, -238],
[0, -217],
[-5, -212],
[-10, -203],
[-24, -196],
[-40, -197],
[-53, -201],
[-57, -204],
[-61, -204],
[-73, -209],
[-86, -212],
[-90, -215],
[-110, -220],
[-119, -224],
[-122, -227],
[-125, -227],
[-145, -237],
[-195, -256],
[-199, -260],
[-199, -266],
[-196, -272],
[-171, -302],
[-168, -310],
[-155, -330],
[-150, -344],
[-147, -346],
],
closed: true,
},
],
],
fillColor: [0.8, 0.7, 0.1],
},
]

const segmentation = [
[
373, 166, 390, 168, 450, 167, 495, 169, 517, 172, 528, 176, 532, 176, 540,
179, 544, 183, 545, 192, 542, 207, 537, 219, 537, 225, 535, 230, 527, 238,
527, 243, 530, 249, 529, 262, 521, 274, 512, 295, 507, 300, 502, 309, 488,
316, 472, 315, 459, 311, 455, 308, 451, 308, 439, 303, 426, 300, 422, 297,
402, 292, 393, 288, 390, 285, 387, 285, 367, 275, 317, 256, 313, 252, 313,
246, 316, 240, 341, 210, 344, 202, 357, 182, 362, 168, 365, 166,
],
]

`

[JinDing123]

function getSegmentationFromPaperJs(
  paperObject,
  imageWidth = 512,
  imageHeight = 512
) {
  // 将 paper_object 导入 Paper.js，转换为 CompoundPath 对象
  const compoundPath = paper.project.importJSON(paperObject)

  // 获取第一个子路径
  const path = compoundPath.children[0] // children[0] 是 Paper.js Path 对象

  // 假设 Paper.js 原点在画布中心，计算偏移量
  const offsetX = imageWidth / 2
  const offsetY = imageHeight / 2

  // 提取 segments 的点坐标，并转换为图像坐标系（正坐标）
  const segmentation = path.segments.map((segment) => [
    segment.point.x + offsetX,
    segment.point.y + offsetY,
  ])

  // 计算边界框 [x_min, y_min, width, height]
  const xs = segmentation.map((point) => point[0])
  const ys = segmentation.map((point) => point[1])
  const xMin = Math.min(...xs)
  const yMin = Math.min(...ys)
  const xMax = Math.max(...xs)
  const yMax = Math.max(...ys)
  const bbox = [xMin, yMin, xMax - xMin, yMax - yMin]

  // 如果需要 COCO 格式的 segmentation（[x1, y1, x2, y2, ...]）
  const cocoSegmentation = segmentation.flat()

  return {
    segmentation: segmentation, // [[x, y], ...]
    cocoSegmentation: [cocoSegmentation], // [x1, y1, x2, y2, ...]
    bbox: bbox, // [x_min, y_min, width, height]
  }
}

Below is a wrongly-written processing function I created. It fails to handle the situation where compoundPath has gaps, as shown in the figure. Such data cannot be processed by this function,However, this kind of data can be processed normally.

This is an example image of erroneous data.It can be seen that there are gaps in the polygon.

This is an example image of normal processed data.

[SixK]

Hello JinDing123, I have no idea if paperjs can be used to achieve the conversion between coco segmentation and compoundPath.
coco dataset .json file is actually done using Python.

[JinDing123]

Thank you for your response. Yes, I also think this conversion is not feasible. However, for other reasons, I still have to implement this function. It's just too difficult.