Negating an image with math_img

The goal of this example is to illustrate the use of the function nilearn.image.math_img on T-maps. We compute a negative image by multiplying its voxel values with -1.

from nilearn import datasets, image, plotting

Retrieve the data: a motor contrast map.

stat_img = datasets.load_sample_motor_activation_image()

Multiply voxel values by -1.

negative_stat_img = image.math_img("-img", img=stat_img)

plotting.plot_stat_map(
    stat_img, cut_coords=(36, -27, 66), threshold=3, title="t-map", vmax=9
)
plotting.plot_stat_map(
    negative_stat_img,
    cut_coords=(36, -27, 66),
    threshold=3,
    title="Negative t-map",
    vmax=9,
)
plotting.show()

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Estimated memory usage: 160 MB