I want to resize and optimize png and jpg image size using wand.
With PIL, I'm able to save the same image with about a 3rd of the size if I specify the optimize option.
with open(filename, 'rb') as f:
pimage = PImage.open(f)
resized_pimage = pimage.resize((scaled_width, scaled_height), PImage.ANTIALIAS) bytes_buffer = io.BytesIO()
resized_pimage.save(bytes_buffer, format="PNG", optimize=True)
However, I'm not sure what the equivalent option for Wand is:
with default_storage.open(filename, 'rb') as f:
img = WImage(file=f)
img.resize(width=scaled_width, height=scaled_height, filter='gaussian')
with WImage(width=scaled_width, height=scaled_height) as png:
png.composite(img, top=0, left=0)
png.format = 'png'
bytes_buffer = io.BytesIO()
png.save(file=bytes_buffer)
I read a few articles about image optimization for ImageMagic (e.g. http://www.smashingmagazine.com/2015/06/efficient-image-resizing-with-imagemagick/) but it is not obvious how I can do these in Wand (I'm a complete newbie in either Wand or PIL).
Any help/pointer would be greatly appreciated.
Updated Answer
Setting the optimization with wand will require some additional MagickWand library extension/configuration. This is due to the quality
attribute needing to be set on the wand
data-structure, and not the image's instance. Confused? I am. Luckily Python's Wand library makes this easy. Try the following.
# Require wand's API library and basic ctypes
from wand.api import library
from ctypes import c_void_p, c_size_t
# Tell Python's wand library about the MagickWand Compression Quality (not Image's Compression Quality)
library.MagickSetCompressionQuality.argtypes = [c_void_p, c_size_t]
# Do work as before
from wand.image import Image
with Image(filename=filename) as img:
img.resize(width=scaled_width, height=scaled_hight)
# Set the optimization level through the linked resources of
# the image instance. (i.e. `wand.image.Image.wand`)
library.MagickSetCompressionQuality(img.wand, 75)
img.save(filename=output_destination)
Original Answer
There are many types of "optimization" for png format, but I'm under the impression your seeking a way to reduce image size.
I believe wand.Image.compression_quality
is what your looking for.
from wand.image import Image
with Image(filename=filename) as img:
img.resize(width=scaled_width, height=scaled_hight)
img.compression_quality = 75
img.save(filename=output_destination)
The above will not reduce quality to 75% as you would expect with the JPEG
format, but instruct which PNG-compression library/algo/filter to use. See PNG compression & Better PNG Compression examples.
+-----+
| 7 5 |
+-----+
| 0 . | Huffman compression (no-zlib)
| 1 . | zlib compression level 1
| 2 . | zlib compression level 2
| 3 . | zlib compression level 3
| 4 . | zlib compression level 4
| 5 . | zlib compression level 5
| 6 . | zlib compression level 6
| 7 . | zlib compression level 7
| 8 . | zlib compression level 8
| 9 . | zlib compression level 9
| . 0 | No data encoding/filtering before compression
| . 1 | "Sub" data encoding/filtering before compression
| . 2 | "Up" data encoding/filtering before compression
| . 3 | "Average" data encoding/filtering before compression
| . 4 | "Paeth" data encoding/filtering before compression
| . 5 | "Adaptive" data encoding/filtering before compression
+-----+
So setting the quality to 75
will compress using zlib level 7
after performing an adaptive
filter. Note this is just the level and filter, not the optimization strategy. The optimization strategy can be set with the CLI option -define png:compression-strategy=zs
however wand has yet to implement image artifact methods.
来源:https://stackoverflow.com/questions/34617422/how-to-optimize-image-size-using-wand-in-python