improve py docs
This commit is contained in:
John Cupitt
parent
2b2bf30fbd
commit
a7766b28b3
|
|
@ -46,13 +46,17 @@
|
|||
|
||||
<listitem>
|
||||
<para>
|
||||
If <code>.new_from_file()</code> fails, the vips overrides
|
||||
have not been found. Make sure <code>Vips.py</code> is in
|
||||
your system overrides area.
|
||||
</para>
|
||||
</listitem>
|
||||
If <code>.new_from_file()</code> fails, the vips overrides
|
||||
have not been found. Make sure <code>Vips.py</code> is in
|
||||
your system overrides area.
|
||||
</para>
|
||||
</listitem>
|
||||
</orderedlist>
|
||||
</para>
|
||||
</refsect3>
|
||||
|
||||
<refsect3 id="python-example">
|
||||
<title>Example program</title>
|
||||
|
||||
<para>
|
||||
Here's a complete example program:
|
||||
|
|
@ -75,8 +79,16 @@ im = im.conv(mask)
|
|||
|
||||
im.write_to_file(sys.argv[2])
|
||||
</programlisting>
|
||||
</para>
|
||||
|
||||
When Python executes the import line:
|
||||
<para>
|
||||
Reading this code, the first interesting line is:
|
||||
|
||||
<programlisting language="Python">
|
||||
from gi.repository import Vips
|
||||
</programlisting>
|
||||
|
||||
When Python executes the import line it performs the following steps:
|
||||
</para>
|
||||
|
||||
<orderedlist>
|
||||
|
|
@ -133,7 +145,13 @@ im.write_to_file(sys.argv[2])
|
|||
</orderedlist>
|
||||
|
||||
<para>
|
||||
The next line loads the input image. You can append
|
||||
The next line is:
|
||||
|
||||
<programlisting language="Python">
|
||||
im = Vips.Image.new_from_file(sys.argv[1])
|
||||
</programlisting>
|
||||
|
||||
This loads the input image. You can append
|
||||
load options to the argument list as keyword arguments, for example:
|
||||
|
||||
<programlisting language="Python">
|
||||
|
|
@ -149,16 +167,32 @@ im = Vips.Image.new_from_file(sys.argv[1], access = Vips.Access.SEQUENTIAL)
|
|||
</para>
|
||||
|
||||
<para>
|
||||
The next line crops 100 pixels off every edge. Try
|
||||
<code>help(im.extract_area)</code> and the C API docs for
|
||||
vips_extract_area() for details. You can use <code>.crop()</code> as a
|
||||
synonym, if you like. <code>im.width</code> gets the image width in
|
||||
pixels, see <code>help(Vips.Image)</code> and vips_image_get_width()
|
||||
The next line is:
|
||||
|
||||
<programlisting language="Python">
|
||||
im = im.extract_area(100, 100, im.width - 200, im.height - 200)
|
||||
</programlisting>
|
||||
|
||||
The arguments are left, top, width, height, so this crops 100 pixels off
|
||||
every edge. Try <code>help(im.extract_area)</code> and the C API docs
|
||||
for vips_extract_area() for details. You can use <code>.crop()</code>
|
||||
as a synonym, if you like.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<code>im.width</code> gets the image width
|
||||
in pixels, see <code>help(Vips.Image)</code> and vips_image_get_width()
|
||||
and friends for a list of the other getters.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The <code>similarity</code> line shrinks by 10%. By default it uses
|
||||
The next line:
|
||||
|
||||
<programlisting language="Python">
|
||||
im = im.similarity(scale = 0.9)
|
||||
</programlisting>
|
||||
|
||||
shrinks by 10%. By default it uses
|
||||
bilinear interpolation, use <code>interpolate</code> to pick another
|
||||
interpolator, for example:
|
||||
|
||||
|
|
@ -166,10 +200,22 @@ im = Vips.Image.new_from_file(sys.argv[1], access = Vips.Access.SEQUENTIAL)
|
|||
im = im.similarity(scale = 0.9, interpolate = Vips.Interpolate.new("bicubic"))
|
||||
</programlisting>
|
||||
|
||||
see vips_similarity() for full documentation. The similarity operator
|
||||
will not give good results for large resizees (more than a factor of
|
||||
two). See vips_resize() if you need to make a large change.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<code>.new_from_array()</code> makes an image from a 2D array. The
|
||||
Next:
|
||||
|
||||
<programlisting language="Python">
|
||||
mask = Vips.Image.new_from_array([[-1, -1, -1],
|
||||
[-1, 16, -1],
|
||||
[-1, -1, -1]], scale = 8)
|
||||
im = im.conv(mask)
|
||||
</programlisting>
|
||||
|
||||
makes an image from a 2D array, then convolves with that. The
|
||||
<code>scale</code> keyword argument lets you set a divisor for
|
||||
convolution, handy for integer convolutions. You can set
|
||||
<code>offset</code> as well. See vips_conv() for details on the vips
|
||||
|
|
@ -177,11 +223,99 @@ im = im.similarity(scale = 0.9, interpolate = Vips.Interpolate.new("bicubic"))
|
|||
</para>
|
||||
|
||||
<para>
|
||||
Finally, <code>.write_to_file()</code> sends the image back to the
|
||||
Finally,
|
||||
|
||||
<programlisting language="Python">
|
||||
im.write_to_file(sys.argv[2])
|
||||
</programlisting>
|
||||
|
||||
sends the image back to the
|
||||
filesystem. There's also <code>.write_to_buffer()</code> to make a
|
||||
string containing the formatted image, and <code>.write()</code> to
|
||||
write to another image.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
As with <code>.new_from_file()</code> you can append save options as
|
||||
keyword arguments. For example:
|
||||
|
||||
<programlisting language="Python">
|
||||
im.write_to_file("test.jpg", Q = 90)
|
||||
</programlisting>
|
||||
|
||||
will write a JPEG image with quality set to 90. See the various save
|
||||
operations for a list of all the save options, for example
|
||||
vips_jpegsave().
|
||||
</para>
|
||||
|
||||
</refsect3>
|
||||
|
||||
<refsect3 id="python-doc">
|
||||
<title>Getting help</title>
|
||||
<para>
|
||||
Try <code>help(Vips)</code> for everything,
|
||||
<code>help(Vips.Image)</code> for something slightly more digestible, or
|
||||
something like <code>help(Vips.Image.black)</code> for help on a
|
||||
specific class member.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
You can't get help on dynamically bound member functions like
|
||||
<code>.add()</code> this way. Instead, make an image and get help
|
||||
from that, for example:
|
||||
|
||||
<programlisting language="Python">
|
||||
image = Vips.Image.new_from_file("x.jpg")
|
||||
help(image.add)
|
||||
</programlisting>
|
||||
|
||||
And you'll get a summary of the operator's behaviour and how the
|
||||
arguments are represented in Python.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The API docs has a <link href="function-list">handy table of all vips
|
||||
operations</link>, if you want to find out how to do something, try
|
||||
searching that.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The <command>vips</command> command can be useful too. For example, in a
|
||||
terminal you can type <command>vips jpegsave</command> to get a
|
||||
summary of an operation:
|
||||
|
||||
<programlisting language="Python">
|
||||
$ vips jpegsave
|
||||
save image to jpeg file
|
||||
usage:
|
||||
jpegsave in filename
|
||||
where:
|
||||
in - Image to save, input VipsImage
|
||||
filename - Filename to save to, input gchararray
|
||||
optional arguments:
|
||||
Q - Q factor, input gint
|
||||
default: 75
|
||||
min: 1, max: 100
|
||||
profile - ICC profile to embed, input gchararray
|
||||
optimize-coding - Compute optimal Huffman coding tables, input gboolean
|
||||
default: false
|
||||
interlace - Generate an interlaced (progressive) jpeg, input gboolean
|
||||
default: false
|
||||
no-subsample - Disable chroma subsample, input gboolean
|
||||
default: false
|
||||
trellis-quant - Apply trellis quantisation to each 8x8 block, input gboolean
|
||||
default: false
|
||||
overshoot-deringing - Apply overshooting to samples with extreme values, input gboolean
|
||||
default: false
|
||||
optimize-scans - Split the spectrum of DCT coefficients into separate scans, input gboolean
|
||||
default: false
|
||||
strip - Strip all metadata from image, input gboolean
|
||||
default: false
|
||||
background - Background value, input VipsArrayDouble
|
||||
operation flags: sequential-unbuffered nocache
|
||||
</programlisting>
|
||||
|
||||
</para>
|
||||
</refsect3>
|
||||
|
||||
<refsect3 id="python-basics">
|
||||
|
|
@ -344,30 +478,6 @@ result_image = image1.bandjoin([image2, 255])
|
|||
</para>
|
||||
</refsect3>
|
||||
|
||||
<refsect3 id="python-doc">
|
||||
<title>Automatic docstrings</title>
|
||||
<para>
|
||||
Try <code>help(Vips)</code> for everything,
|
||||
<code>help(Vips.Image)</code> for something slightly more digestible, or
|
||||
something like <code>help(Vips.Image.black)</code> for help on a
|
||||
specific class member.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
You can't get help on dynamically bound member functions like
|
||||
<code>.add()</code> this way. Instead, make an image and get help
|
||||
from that, for example:
|
||||
|
||||
<programlisting language="Python">
|
||||
image = Vips.Image.new_from_file("x.jpg")
|
||||
help(image.add)
|
||||
</programlisting>
|
||||
|
||||
And you'll get a summary of the operator's behaviour and how the
|
||||
arguments are represented in Python. Use the C API docs for more detail.
|
||||
</para>
|
||||
</refsect3>
|
||||
|
||||
<refsect3 id="python-exceptions">
|
||||
<title>Exceptions</title>
|
||||
<para>
|
||||
|
|
|
|||
Loading…
Reference in New Issue