Libvips: web api performance issues

[volkan]

Hi,

I want to use web api for pyvips.
But realy bad performance. Where do I make mistakes?

My code is following;

hello.py

from flask import Flask
from Image import ImageTransform
from flask import request
from flask import send_file
import io

app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

@app.route("/image")
def image():
    image_value = request.args.get('image')
    i = ImageTransform(image_value)
    i.set_transform()
    a = i.image.write_to_buffer('.jpeg')
    return send_file(io.BytesIO(a), mimetype='image/jpg')

Image.py

import pyvips
import math

class ImageTransform(object):
    image = None

    def __init__(self, file_name):
        self.image = pyvips.Image.new_from_file(file_name, access='sequential')

    def set_resize_transform(self, width, height):
        im = self.image
        mem = im.write_to_buffer('.jpeg[Q=80]')
        im = pyvips.Image.thumbnail_buffer(mem, width, height=height)

        im = im.bandjoin(255)
        im = im.gravity("centre", width, height,
                            extend="background",
                            background=[244, 244, 244, 255])
        self.image = im                            
        pass
    def set_ratio_and_watermark_transform(self):
        im = self.image
        # ##### ######
        # Trigonometry: Tangent = Opposite / Adjacent
        tangent = im.height/im.width
        # convert arctangent to degrees
        angle = math.atan(tangent)*(180/math.pi);

        water_mark_x = 140
        water_mark_y = 140
        water_mark_len = 16
        # a^2 = b^2 + c^2 ; a = sqrt(b^2 + c^2)
        half_hypotenuse = math.sqrt(im.height*im.height + im.width*im.width)/2;
        font_size = int(math.hypot(im.height, im.width)/math.hypot(water_mark_x, water_mark_y)*(4 + int(water_mark_len/2)))

        text = pyvips.Image.text("text text text", font = "Futura Medium", align='centre', width = 500, dpi = (font_size*4))
        text = text.linear(0.3, 0)

        text = text.similarity(angle=angle)

        x = (im.width-text.width)/2
        y = (im.height-text.height)/2

        text = text.embed(x, y, text.width + x, text.height + y, extend="copy")

        w = im.width if text.width > im.width else text.width
        h = im.height if text.height > im.height else text.height

        im = text.ifthenelse(255, im, blend=True)      
        self.image = im

    def set_transform(self, type=int):
        self.set_ratio_and_watermark_transform()
        self.set_resize_transform(600, 450)

    def write_image(self,dest_name):
        self.image.write_to_file(dest_name)

```bash
FLASK_APP=hello.py flask run

```bash
ab -c 10 -n 10 http://54.229.246.74/image\?image\=foto.jpeg

[jcupitt]

Hello @volkan,

I would reorganise your pipeline to something like:

1. Use thumbnail to open the image and downsize in one operation
2. Add the watermark overlay
3. Finally, use gravity to add the background

I'll make an example for you.

[jcupitt]

Here's a test program that runs your code and a possible new pipeline. I changed the tangent line in your version to:

        tangent = float(im.width) / im.height

But otherwise unaltered.

import time
import sys
import math
import pyvips

from Image import ImageTransform

start = time.time()
i = ImageTransform(sys.argv[1])
i.set_transform()
i.write_image(sys.argv[2])
end = time.time()
print "ImageTransform() took ", end - start

start = time.time()

target_width = 600
target_height = 450         

# efficiently load and downsize in one operation
im = pyvips.Image.thumbnail(sys.argv[1], target_width, height=target_height)

# watermark
tangent = float(im.width) / im.height
angle = math.atan(tangent) * (180 / math.pi)
water_mark_x = 140
water_mark_y = 140
water_mark_len = 16
half_hypotenuse = math.sqrt(im.height*im.height + im.width*im.width)/2;
font_size = int(math.hypot(im.height, im.width)/math.hypot(water_mark_x, water_mark_y)*(4 + int(water_mark_len/2)))
text = pyvips.Image.text("text text text", font = "Futura Medium", align='centre', width = 500, dpi = (font_size*4))
text = text.linear(0.3, 0)
text = text.similarity(angle=angle)
x = (im.width - text.width) / 2
y = (im.height - text.height) / 2
text = text.embed(x, y, text.width + x, text.height + y, extend="copy")
w = im.width if text.width > im.width else text.width
h = im.height if text.height > im.height else text.height
im = text.ifthenelse(255, im, blend=True)  

# add alpha and margins
im = im.bandjoin(255)
im = im.gravity("centre", target_width, target_height,
                    extend="background",
                    background=[244, 244, 244, 255])

im.write_to_file(sys.argv[2])

end = time.time()

print "after revision, took ", end - start

On this laptop with a 6k x 4k image, I see:

$ python volkan.py ~/pics/theo.jpg x.jpg
ImageTransform() took  0.490525960922
after revision, took  0.0774891376495

You could make your watermark code a little simpler, I'll have a go.

[jcupitt]

I think I'd add the watermark like this:

# in libvips 8.6, you can get text to automatically size to fill a rectangle
text = pyvips.Image.text("text text text", 
                         font="Futura Medium", align="centre", 
                         width=300, height=300)  

# scale down brightness, then back to 8 bit ... this will avoid float arithmetic
# for the rotate/expand/ifthenelse
text = (text * 0.3).cast("uchar")

tangent = float(im.width) / im.height
angle = math.atan(tangent) * (180 / math.pi)
text = text.similarity(angle=angle)
text = text.gravity("centre", target_width, target_height)

im = text.ifthenelse(255, im, blend=True) 

So that's using the new "size text to fit box" feature in 8.6, using x * 0.3 instead of linear (they do the same thing, the operator overload is just easier to read), keeping the text as 8-bit to avoid float later, and using gravity to make the embed a bit simpler.

[volkan]

@jcupitt your examples very helpful. Thanks.

[jcupitt]

OK, I'll close!