write_mesh.json

The JSON file of the “Four kinds of mesh, every corner its own colour” example. Six triangles round a centre they share, their edges stroked over the paint; a lattice of points in the four printing inks; a patch whose four sides are curves; and the same patch pulled about by four points inside it.

JSON 396 lines

This file is a request: an application sends it over the network to the server, which creates the PDF and sends it back. It makes the same page as the Rust and Python versions of this example. A request names every file it uses, never its content; the call carries the request and the files together. A font the server already holds, such as DejaVuSans, is named with nothing attached. Send the request to the address the API page gives.

What this example is for

A gradient runs in a straight line or out from a point, and that covers most of what a page asks for. It does not cover a background whose colour turns a corner, a map shaded from readings taken in twenty places, or a picture of heat where every spot has its own value. The usual way out is to build the picture in a drawing program and drop it in — and then it is a photograph of colour: heavy inside the file, fixed at the size it was made at, and soft at the edges the moment somebody prints the page larger.

What this example shows

Download the file The same example in Rust The same example in Python See what it creates 
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{
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        {"curve_to": {"x1": 145.0, "y1": 500.0, "x2": 205.0, "y2": 460.0, "x": 260.0, "y": 480.0}},
        {"curve_to": {"x1": 280.0, "y1": 425.0, "x2": 240.0, "y2": 375.0, "x": 260.0, "y": 320.0}},
        {"curve_to": {"x1": 205.0, "y1": 300.0, "x2": 145.0, "y2": 340.0, "x": 90.0, "y": 320.0}},
        "close"
      ]
    },
    {
      "type": "text",
      "rect": {"llx": 70.0, "lly": 285.0, "urx": 280.0, "ury": 297.0},
      "content": ["A Coons patch: four curved sides"],
      "font": "DejaVuSans",
      "font_size": 10.0
    },
    {
      "type": "rect",
      "rect": {"llx": 310.0, "lly": 295.0, "urx": 530.0, "ury": 505.0},
      "fill": {"shading": "tensor"}
    },
    {
      "type": "path",
      "stroke": {"width": 0.6, "color": [0.3, 0.3, 0.3]},
      "segments": [
        {"move_to": {"x": 335.0, "y": 320.0}},
        {"curve_to": {"x1": 315.0, "y1": 375.0, "x2": 355.0, "y2": 425.0, "x": 335.0, "y": 480.0}},
        {"curve_to": {"x1": 390.0, "y1": 500.0, "x2": 450.0, "y2": 460.0, "x": 505.0, "y": 480.0}},
        {"curve_to": {"x1": 525.0, "y1": 425.0, "x2": 485.0, "y2": 375.0, "x": 505.0, "y": 320.0}},
        {"curve_to": {"x1": 450.0, "y1": 300.0, "x2": 390.0, "y2": 340.0, "x": 335.0, "y": 320.0}},
        "close"
      ]
    },
    {
      "type": "text",
      "rect": {"llx": 315.0, "lly": 285.0, "urx": 525.0, "ury": 297.0},
      "content": ["A tensor patch: same sides, pulled inside"],
      "font": "DejaVuSans",
      "font_size": 10.0
    },
    {
      "type": "text",
      "rect": {"llx": 70.0, "lly": 100.0, "urx": 525.0, "ury": 265.0},
      "content": [
        "Every point above carries a place and a colour, and the colour between points is worked out from the points around it. The six triangles at the top left each name their own three corners, so the centre they share is stated six times over: that is what lets a free-form mesh take any shape at all, and their edges are stroked over the paint so they can be counted. The lattice beside them states each point once, row after row, and the grid says which points make a triangle: forty-two points make sixty triangles, here in cyan, magenta, yellow and black, which is what a press is given. The two patches at the bottom bend their four sides into curves and carry a colour at each of their four corners. The Coons patch works its inside out from those sides alone; the tensor-product patch beside it has the same sides and the same corners, and four more points inside it pull its colours towards the top right."
      ],
      "font": "DejaVuSans",
      "font_size": 8.5,
      "leading": 12.0,
      "color": [0.35, 0.35, 0.35]
    }
  ]
}