# read patch via fetch
bands = 3
vips_image = pyvips.Image.new_from_file(vips_filename=fpath, level=level, rgb=True)
region = pyvips.Region.new(vips_image)
patch_fetch = region.fetch(location[0], location[1], size[0], size[1])
patch_fetch = np.ndarray(buffer=patch_fetch,
                         dtype=np.uint8,
                         shape=(size[1], size[0], bands))

#!/usr/bin/python3

# makes 12,512 patches in 0.5s from CMU-1-Small-region.svs

import sys
import pyvips

def fetch(region, patch_size, x, y):
    return region.fetch(patch_size * x, patch_size * y, patch_size, patch_size)

image[0] = pyvips.Image.new_from_file(sys.argv[1], rgb=True)
image[1] = image0.rot90()
image[2] = image0.rot180()
image[3] = image0.rot270()

image[4] = image[0].fliphor()
image[5] = image[4].rot90()
image[6] = image[4].rot180()
image[7] = image[4].rot270()

reg = [pyvips.Region.new(x) for x in image]

patch_size = 64
n_across = image0.width // patch_size
n_down = image0.height // patch_size
x_max = n_across - 1
y_max = n_down - 1

n_patches = 0
for y in range(0, n_down):
    print("row {} ...".format(y))
    for x in range(0, n_across):
        patch0 = fetch(reg[0], patch_size, x, y)
        patch1 = fetch(reg[1], patch_size, y_max - y, x)
        patch2 = fetch(reg[2], patch_size, x_max - x, y_max - y)
        patch3 = fetch(reg[3], patch_size, y, x_max - x)

        patch4 = fetch(reg[4], patch_size, x_max - x, y)
        patch5 = fetch(reg[5], patch_size, y_max - y, x_max - x)
        patch6 = fetch(reg[6], patch_size, x, y_max - y)
        patch7 = fetch(reg[7], patch_size, y, x)

        n_patches += 8

print("{} patches generated".format(n_patches))

bands = 4 # 4 not 3 since RGBA!
vips_image = pyvips.Image.new_from_file(vips_filename=fpath, level=level)
region = pyvips.Region.new(vips_image)
patch_fetch = region.fetch(location[0], location[1], size[0], size[1])
patch_fetch = np.ndarray(buffer=patch_fetch,
                         dtype=np.uint8,
                         shape=(size[1], size[0], bands))
patch_fetch = patch_fetch[:,: , 0:3]

vips_image = pyvips.Image.new_from_file(vips_filename=fpath, level=level, rgb=True)

---------------------------------------------------------------------------
Error                                     Traceback (most recent call last)
Cell In[4], line 1
----> 1 vips_image = pyvips.Image.new_from_file(vips_filename=fpath, level=level, rgb=True)

File ~/anaconda3/envs/cpath/lib/python3.8/site-packages/pyvips/vimage.py:352, in Image.new_from_file(vips_filename, **kwargs)
    349     raise Error('unable to load from file {0}'.format(vips_filename))
    350 name = _to_string(pointer)
--> 352 return pyvips.Operation.call(name, filename,
    353                              string_options=options, **kwargs)

File ~/anaconda3/envs/cpath/lib/python3.8/site-packages/pyvips/voperation.py:288, in Operation.call(operation_name, *args, **kwargs)
    285 for name in kwargs:
    286     if (name not in intro.optional_input and
    287             name not in intro.optional_output):
--> 288         raise Error('{0} does not support optional argument {1}'
    289                     .format(operation_name, name))
    291     value = kwargs[name]
    292     details = intro.details[name]

Error: VipsForeignLoadOpenslideFile does not support optional argument rgb