How to use pyvips - 10 common examples

def test_histfind_indexed(self):
        im = pyvips.Image.black(50, 100)
        test = im.insert(im + 10, 50, 0, expand=True)
        index = test // 10

        for x in noncomplex_formats:
            for y in [pyvips.BandFormat.UCHAR, pyvips.BandFormat.USHORT]:
                a = test.cast(x)
                b = index.cast(y)
                hist = a.hist_find_indexed(b)

                assert_almost_equal_objects(hist(0, 0), [0])
                assert_almost_equal_objects(hist(1, 0), [50000])

# wrap VipsImage

from __future__ import division

import numbers

import pyvips
from pyvips import ffi, glib_lib, vips_lib, Error, _to_bytes, \
    _to_string, GValue

ffi.cdef('''
    typedef struct _VipsImage {
        VipsObject parent_instance;

        // opaque
    } VipsImage;

    const char* vips_foreign_find_load (const char* name);
    const char* vips_foreign_find_load_buffer (const void* data, size_t size);
    const char* vips_foreign_find_save (const char* name);
    const char* vips_foreign_find_save_buffer (const char* suffix);

    VipsImage* vips_image_new_matrix_from_array (int width, int height,
            const double* array, int size);
    VipsImage* vips_image_new_from_memory (const void* data, size_t size,
            int width, int height, int bands, int format);

def test_array_image(self):
        image = pyvips.Image.new_from_file(JPEG_FILE)
        r, g, b = image.bandsplit()
        gv = pyvips.GValue()
        gv.set_type(pyvips.GValue.array_image_type)
        gv.set([r, g, b])
        value = gv.get()
        assert value, [r, g == b]

def test_array_image(self):
        image = pyvips.Image.new_from_file(JPEG_FILE)
        r, g, b = image.bandsplit()
        gv = pyvips.GValue()
        gv.set_type(pyvips.GValue.array_image_type)
        gv.set([r, g, b])
        value = gv.get()
        assert value, [r, g == b]

def test_premultiply(self):
        for fmt in unsigned_formats + [pyvips.BandFormat.SHORT,
                                       pyvips.BandFormat.INT] + float_formats:
            mx = 255
            alpha = mx / 2.0
            test = self.colour.bandjoin(alpha).cast(fmt)
            pixel = test(30, 30)

            predict = [int(x) * alpha / mx for x in pixel[:-1]] + [alpha]

            im = test.premultiply()

            assert im.bands == test.bands
            pixel = im(30, 30)
            for x, y in zip(pixel, predict):
                # we use float arithetic for int and uint, so the rounding
                # differs ... don't require huge accuracy
                assert abs(x - y) < 2

def test_unpremultiply(self):
        for fmt in unsigned_formats + [pyvips.BandFormat.SHORT,
                                       pyvips.BandFormat.INT] + float_formats:
            mx = 255
            alpha = mx / 2.0
            test = self.colour.bandjoin(alpha).cast(fmt)
            pixel = test(30, 30)

            predict = [int(x) / (alpha / mx) for x in pixel[:-1]] + [alpha]

            im = test.unpremultiply()

            assert im.bands == test.bands
            pixel = im(30, 30)
            for x, y in zip(pixel, predict):
                # we use float arithetic for int and uint, so the rounding
                # differs ... don't require huge accuracy
                assert abs(x - y) < 2

def test_vips(self):
        self.save_load_file(".v", "", self.colour, 0)

        # check we can save and restore metadata
        filename = temp_filename(self.tempdir, ".v")
        self.colour.write_to_file(filename)
        x = pyvips.Image.new_from_file(filename)
        before_exif = self.colour.get("exif-data")
        after_exif = x.get("exif-data")

        assert len(before_exif) == len(after_exif)
        for i in range(len(before_exif)):
            assert before_exif[i] == after_exif[i]

        x = None

def test_rotate(self):
        if have("rotate"):
            im = pyvips.Image.new_from_file(JPEG_FILE)
            im2 = im.rotate(90)
            im3 = im.affine([0, -1, 1, 0])
            # rounding in calculating the affine transform from the angle stops
            # this being exactly true
            assert (im2 - im3).abs().max() < 50

def test_stream(self):
        streami = pyvips.Streami.new_from_file(JPEG_FILE)
        image = pyvips.Image.new_from_stream(streami, '', access='sequential')
        filename = temp_filename(self.tempdir, '.png')
        streamo = pyvips.Streamo.new_to_file(filename)
        image.write_to_stream(streamo, '.png')

        image = pyvips.Image.new_from_file(JPEG_FILE, access='sequential')
        image2 = pyvips.Image.new_from_file(filename, access='sequential')

        assert (image - image2).abs().max() < 10

def test_heifsave(self):
        self.save_load_buffer("heifsave_buffer", "heifload_buffer",
                              self.colour, 80)
        self.save_load("%s.heic", self.colour)

        # test lossless mode
        im = pyvips.Image.new_from_file(HEIC_FILE)
        buf = im.heifsave_buffer(lossless=True)
        im2 = pyvips.Image.new_from_buffer(buf, "")
        # not in fact quite lossless
        assert abs(im.avg() - im2.avg()) < 3

        # higher Q should mean a bigger buffer
        b1 = im.heifsave_buffer(Q=10)
        b2 = im.heifsave_buffer(Q=90)
        assert len(b2) > len(b1)

        # try saving an image with an ICC profile and reading it back 
        # not all libheif have profile support, so put it in an if
        buf = self.colour.heifsave_buffer()
        im = pyvips.Image.new_from_buffer(buf, "")
        p1 = self.colour.get("icc-profile-data")
        if im.get_typeof("icc-profile-data") != 0: