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238 | """Lays every image the tests ship with on one page, each captioned with what the
file itself declares.
The Python twin of the `write_image_gallery` example in Rust.
Nothing in the captions is written by hand: each line is read back out of the image
after it was parsed, so the page is a statement of what the library understood rather
than of what the example was told. A file that declares nothing says so, which is the
point of showing it next to the ones that do.
Usage: python examples/write_image_gallery.py [out.pdf] [font.ttf]
"""
from __future__ import annotations
from pathlib import Path
import _licence
import _out
import hqf_pdf
# Every image committed for the tests.
IMAGES = Path(__file__).resolve().parents[2] / "hqf-pdf" / "tests" / "images"
# The page, and the grid laid over it.
MARGIN = 30.0
COLUMNS = 4
ROWS = 5
# The tallest and widest a thumbnail is drawn.
THUMBNAIL = (110.0, 92.0)
# The caption under each thumbnail.
CAPTION_SIZE = 5.6
CAPTION_LEADING = 7.4
# Ink.
TEXT = hqf_pdf.Rgb(0.15, 0.16, 0.2)
FADED = hqf_pdf.Rgb(0.42, 0.44, 0.5)
TILE = hqf_pdf.Rgb(0.95, 0.96, 0.97)
# The way up an ``Exif`` header names by its number, in words.
WAYS_UP = {
2: "mirrored left to right",
3: "upside down",
4: "mirrored top to bottom",
5: "mirrored, turned left",
6: "turned right",
7: "mirrored, turned right",
8: "turned left",
}
def colour_of(image: hqf_pdf.Image) -> str:
"""What one pixel of the image stands for, in the fewest words that still say it."""
palette = image.color_space.palette
if palette is not None:
return f"a table of {len(palette) // 3} colours"
return {1: "grey", 3: "red, green, blue", 4: "four inks"}.get(
image.color_space.components, "colours of some other kind"
)
def facts(image: hqf_pdf.Image) -> list[str]:
"""What the file says about itself, one statement at a time.
A file that says nothing beyond its shape says so: the point of the page is that
both kinds sit side by side.
"""
bits = image.bits_per_component
facts = [
f"{image.width} by {image.height} pixels",
colour_of(image),
f"{bits} bit" if bits == 1 else f"{bits} bits",
]
stated = []
resolution = image.resolution
if resolution is not None:
stated.append(f"{resolution.x:.0f} by {resolution.y:.0f} dots to the inch")
orientation = image.orientation
if orientation is not None:
stated.append(f"seen {WAYS_UP.get(orientation.tag, 'the way it is stored')}")
if image.has_alpha:
stated.append("opacity per pixel")
if image.color_key is not None:
stated.append("one colour left out")
if image.icc_profile is not None:
stated.append("read through sRGB")
facts.extend(stated if stated else ["declaring nothing else of itself"])
return facts
def packed(font: hqf_pdf.FontHandle, width: float, statements: list[str]) -> list[str]:
"""The statements laid end to end, broken into lines that fit ``width``.
Nothing is dropped: a caption that will not fit on one line takes as many as it
needs, which is what keeps the page a full account of what was read.
"""
lines: list[str] = []
for statement in statements:
joined = f"{lines[-1]}, {statement}" if lines else ""
if lines and font.measure(joined, CAPTION_SIZE) <= width:
lines[-1] = joined
else:
lines.append(statement)
return lines
def text(
content: hqf_pdf.Content,
font: hqf_pdf.FontHandle,
size: float,
at: tuple[float, float],
colour: hqf_pdf.Rgb,
s: str,
) -> None:
"""Draws a line of text, left-aligned, in a colour of its own."""
content.set_fill(colour)
content.draw_text(font, size, at[0], at[1], s)
def text_fitted(
content: hqf_pdf.Content,
font: hqf_pdf.FontHandle,
size: float,
at: tuple[float, float],
width: float,
colour: hqf_pdf.Rgb,
s: str,
) -> None:
"""Draws a line of text, shortened until it fits the width it is given."""
line = s
while font.measure(line, size) > width and len(line) > 1:
line = line[:-2] + "…"
text(content, font, size, at, colour, line)
def tile(
content: hqf_pdf.Content,
font: hqf_pdf.FontHandle,
handle: hqf_pdf.ImageHandle,
lines: list[str],
at: tuple[float, float],
cell: tuple[float, float],
) -> None:
"""Draws one tile: the picture inside its box, and what the file says under it."""
x, y = at
cell_width, cell_height = cell
caption_height = CAPTION_LEADING * len(lines)
box_height = cell_height - caption_height - 6.0
content.set_fill(TILE)
content.rect(x, y + caption_height + 6.0, cell_width, box_height)
content.fill()
# The picture keeps its proportions inside the box, and sits in the middle of it.
width, height = handle.fit_within(min(THUMBNAIL[0], cell_width - 8.0), THUMBNAIL[1])
content.draw_image(
handle,
x + (cell_width - width) / 2.0,
y + caption_height + 6.0 + (box_height - height) / 2.0,
width,
height,
)
for index, line in enumerate(lines):
colour = TEXT if index == 0 else FADED
text_fitted(
content,
font,
CAPTION_SIZE,
(x, y + caption_height - CAPTION_LEADING * (index + 1) + 2.0),
cell_width,
colour,
line,
)
def main() -> None:
out = _out.output_path("image_gallery")
document = hqf_pdf.Document()
document.set_license(_licence.licensed())
document.set_info("Title", "hqf-pdf image gallery")
font = document.add_font(hqf_pdf.Font.from_path(_out.font_path()))
page = hqf_pdf.Page.a4()
cell_width = (page.width - 2.0 * MARGIN) / COLUMNS - 6.0
tiles = []
for path in sorted(path for path in IMAGES.iterdir() if path.is_file()):
image = hqf_pdf.Image.from_path(path)
lines = [path.name, *packed(font, cell_width, facts(image))]
tiles.append((document.add_image(image), lines))
content = hqf_pdf.Content()
text(
content,
font,
13.0,
(MARGIN, page.height - MARGIN - 10.0),
TEXT,
"Every picture the tests ship with, and what each file says about itself",
)
top = page.height - MARGIN - 34.0
cell_height = (top - MARGIN) / ROWS
for index, (handle, lines) in enumerate(tiles):
column, row = index % COLUMNS, index // COLUMNS
if row >= ROWS:
print(
f"{len(tiles)} pictures do not fit on one page; the rest are left off"
)
break
tile(
content,
font,
handle,
lines,
(MARGIN + (cell_width + 6.0) * column, top - cell_height * (row + 1)),
(cell_width, cell_height - 6.0),
)
page.set_content(content)
document.add_page(page)
written = document.write(out)
print(f"wrote {out}: {written} bytes, {len(tiles)} pictures")
if __name__ == "__main__":
main()
|