NUmpy and matplotlib.tri.triangulation to Geotiff in Python

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1

I have unstructured data i want to make geotiff plot using triangulation(trimesh). I am able to generate png plot but i want to generate geotiff, Can you please let me know how to generate geotiff plot in python. I want GEOTIFF using rasterio or matplotlib or other module, My code you can find below which is generating png matplotlib plot.

```
def plot():
    import matplotlib.tri as mtri
    import numpy as np
    import pandas as pd
    import matplotlib.pyplot as plt

    # Some points defining a triangulation over (roughly) Britain.
    xy = np.asarray([
        [-0.101, 0.872], [-0.080, 0.883], [-0.069, 0.888], [-0.054, 0.890],
        [-0.045, 0.897], [-0.057, 0.895], [-0.073, 0.900], [-0.087, 0.898],
        [-0.090, 0.904], [-0.069, 0.907], [-0.069, 0.921], [-0.080, 0.919],
        [-0.073, 0.928], [-0.052, 0.930], [-0.048, 0.942], [-0.062, 0.949],
        [-0.054, 0.958], [-0.069, 0.954], [-0.087, 0.952], [-0.087, 0.959],
        [-0.080, 0.966], [-0.085, 0.973], [-0.087, 0.965], [-0.097, 0.965],
        [-0.097, 0.975], [-0.092, 0.984], [-0.101, 0.980], [-0.108, 0.980],
        [-0.104, 0.987], [-0.102, 0.993], [-0.115, 1.001], [-0.099, 0.996],
        [-0.101, 1.007], [-0.090, 1.010], [-0.087, 1.021], [-0.069, 1.021],
        [-0.052, 1.022], [-0.052, 1.017], [-0.069, 1.010], [-0.064, 1.005],
        [-0.048, 1.005], [-0.031, 1.005], [-0.031, 0.996], [-0.040, 0.987],
        [-0.045, 0.980], [-0.052, 0.975], [-0.040, 0.973], [-0.026, 0.968],
        [-0.020, 0.954], [-0.006, 0.947], [0.003, 0.935], [0.006, 0.926],
        [0.005, 0.921], [0.022, 0.923], [0.033, 0.912], [0.029, 0.905],
        [0.017, 0.900], [0.012, 0.895], [0.027, 0.893], [0.019, 0.886],
        [0.001, 0.883], [-0.012, 0.884], [-0.029, 0.883], [-0.038, 0.879],
        [-0.057, 0.881], [-0.062, 0.876], [-0.078, 0.876], [-0.087, 0.872],
        [-0.030, 0.907], [-0.007, 0.905], [-0.057, 0.916], [-0.025, 0.933],
        [-0.077, 0.990], [-0.059, 0.993]])
    # Make lats + lons
    x = abs(xy[:, 0] * 180 / 3.14159)
    y = xy[:, 1] * 180 / 3.14159

    # A selected triangulation of the points.
    triangles = np.asarray([
        [67, 66, 1], [65, 2, 66], [1, 66, 2], [64, 2, 65], [63, 3, 64],
        [60, 59, 57], [2, 64, 3], [3, 63, 4], [0, 67, 1], [62, 4, 63],
        [57, 59, 56], [59, 58, 56], [61, 60, 69], [57, 69, 60], [4, 62, 68],
        [6, 5, 9], [61, 68, 62], [69, 68, 61], [9, 5, 70], [6, 8, 7],
        [4, 70, 5], [8, 6, 9], [56, 69, 57], [69, 56, 52], [70, 10, 9],
        [54, 53, 55], [56, 55, 53], [68, 70, 4], [52, 56, 53], [11, 10, 12],
        [69, 71, 68], [68, 13, 70], [10, 70, 13], [51, 50, 52], [13, 68, 71],
        [52, 71, 69], [12, 10, 13], [71, 52, 50], [71, 14, 13], [50, 49, 71],
        [49, 48, 71], [14, 16, 15], [14, 71, 48], [17, 19, 18], [17, 20, 19],
        [48, 16, 14], [48, 47, 16], [47, 46, 16], [16, 46, 45], [23, 22, 24],
        [21, 24, 22], [17, 16, 45], [20, 17, 45], [21, 25, 24], [27, 26, 28],
        [20, 72, 21], [25, 21, 72], [45, 72, 20], [25, 28, 26], [44, 73, 45],
        [72, 45, 73], [28, 25, 29], [29, 25, 31], [43, 73, 44], [73, 43, 40],
        [72, 73, 39], [72, 31, 25], [42, 40, 43], [31, 30, 29], [39, 73, 40],
        [42, 41, 40], [72, 33, 31], [32, 31, 33], [39, 38, 72], [33, 72, 38],
        [33, 38, 34], [37, 35, 38], [34, 38, 35], [35, 37, 36]])
    z = np.random.uniform(0, 16, 74)
    triangles = np.asarray([
        [67, 66, 1], [65, 2, 66], [1, 66, 2], [64, 2, 65], [63, 3, 64],
        [60, 59, 57], [2, 64, 3], [3, 63, 4], [0, 67, 1], [62, 4, 63],
        [57, 59, 56], [59, 58, 56], [61, 60, 69], [57, 69, 60], [4, 62, 68],
        [6, 5, 9], [61, 68, 62], [69, 68, 61], [9, 5, 70], [6, 8, 7],
        [4, 70, 5], [8, 6, 9], [56, 69, 57], [69, 56, 52], [70, 10, 9],
        [54, 53, 55], [56, 55, 53], [68, 70, 4], [52, 56, 53], [11, 10, 12],
        [69, 71, 68], [68, 13, 70], [10, 70, 13], [51, 50, 52], [13, 68, 71],
        [52, 71, 69], [12, 10, 13], [71, 52, 50], [71, 14, 13], [50, 49, 71],
        [49, 48, 71], [14, 16, 15], [14, 71, 48], [17, 19, 18], [17, 20, 19],
        [48, 16, 14], [48, 47, 16], [47, 46, 16], [16, 46, 45], [23, 22, 24],
        [21, 24, 22], [17, 16, 45], [20, 17, 45], [21, 25, 24], [27, 26, 28],
        [20, 72, 21], [25, 21, 72], [45, 72, 20], [25, 28, 26], [44, 73, 45],
        [72, 45, 73], [28, 25, 29], [29, 25, 31], [43, 73, 44], [73, 43, 40],
        [72, 73, 39], [72, 31, 25], [42, 40, 43], [31, 30, 29], [39, 73, 40],
        [42, 41, 40], [72, 33, 31], [32, 31, 33], [39, 38, 72], [33, 72, 38],
        [33, 38, 34], [37, 35, 38], [34, 38, 35], [35, 37, 36]])
    x = abs(xy[:, 0] * 180 / 3.14159)
    y = xy[:, 1] * 180 / 3.14159

    triang = mtri.Triangulation(x, y, triangles=triangles)
    print("type(triang):", triang)
    print("type(z):", type(z))

    ax=plt.tripcolor(triang,z,vmin=0,vmax=2)
    ax
    plt.show(ax)
    plt.savefig(ax,"ax.png")
plot()
```

Thank You

2

matplotlib does not natively support writing geotiffs, so you might want to try constructing one from your boundaries directly using RasterIO:
https://rasterio.readthedocs.io/en/latest/topics/features.html

3

thank you, rasterio is a only module wch will help me creating geotiff image isnt it ? In Rasterio the problem is coming that i have unstructured data and trigulation mesh wch is not straight forward, :frowning:

4

sorry for late reply ,
My final output is that i have latitude , longitude and one parameter value , these are unstructure data so with help of trigulation i am creating trimesh (triangulation mesh) ,
with help of latitude longitude and node value i am able to create the trigulation mesh on that triangulation mesh i am plotting z parameter value ,
Now this total plot geotiff i want to create ,
I am able to create png with help of matplotlib but i don’'t know how to create geotiff of this plot , as per i know geotiff contain latitude and longitude which is not present in simple png plot image.

5

I am able to convert my png plot to tiff but only 2 color are coming white and black ,
Things i need / output required :-
1- As like my png color my geotiff color come.
2-Only Polygon part should be present in geotiff no boundary

Below is my Png plot.
image

Below is the code to convert the png to geotiff
import pprint
import rasterio
from rasterio import features

with rasterio.open("ax.png") as src:
    blue=src.read(3)
mask=blue!=255
shapes=features.shapes(blue,mask=mask,transform=src.transform)
pprint.pprint(next(shapes))

image = features.rasterize(
            ((g, 255) for g, v in shapes),
            out_shape=src.shape,
            transform=src.transform)

print(image)
with rasterio.open(
        'rasterized-results3.tif', 'w',
        driver='GTiff',
        dtype=rasterio.uint8,
        count=1,
        width=src.width,
        height=src.height) as dst:
    dst.write(image, indexes=1)
print("End Line.")
6

contd.
Below is the geotiff plot output which is generated using above code
image

7

Sorry but your question is outside the scope of Matplotlib. Maybe a library specific to your use case like https://trimsh.org/index.html might be of more use? Or asking on a GIS forum?

8

okay,
can you help me in converting png to geotiff process ?
Any link which through which i can convert my png wch is generated by matplotlib to geotiff ?

9

Hi,
where i can get where is gis forum , any link?
step to use gis forum