Displaying a RGB image in float64

Question

I have an image with data type uint8. I want to convert it to the data type float64 and display it. I expected to see the image as I displayed it with data type uint8. But the result is this:

My original image is like this:

Why is this happening? How can I fix it?

Asked By: Mina

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Source

Answer 1

Even you can use float numbers to process your RGB image, matplotlib accepts only 3 input formats:

Xarray-like or PIL image
The image data. Supported array shapes are:

(M, N): an image with scalar data. The values are mapped to colors using normalization and a colormap. See parameters norm, cmap, vmin, vmax.

(M, N, 3): an image with RGB values (0-1 float or 0-255 int).

(M, N, 4): an image with RGBA values (0-1 float or 0-255 int), i.e. including transparency.

The first two dimensions (M, N) define the rows and columns of the image.
Out-of-range RGB(A) values are clipped.

The important keys are:

0-1 float or 0-255 int
Out-of-range RGB(A) values are clipped.

So if you want to display an image with float numbers, you have to divide the image array by 255.

img_int = np.random.randint(0, 256, (32, 32, 3))
img_float = img_int / 255

fig, (ax1, ax2) = plt.subplots(1, 2, figsize=(8, 4))
ax1.imshow(img_int)
ax2.imshow(img_float)
plt.show()

Output:

Answered By: Corralien

Displaying a RGB image in float64

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