I found a so wired thing while converting a pdf to jpeg, so i'd like to figure out that maybe this is a small bug. See the converted jpg below, you could find that, the background color are all black. The image is here: www.shdowin.com/public/02.jpg
However, in the source file of pdf, you can see that the background color are normal white. The image is here: www.shdowin.com/public/normal.jpg
I thought this maybe my pdf file's fault, however, when i try to use Acrobat.pdf2image in .NET environment, the converted jpg shows correctly.
Here is my code:
from wand.image import Image
from wand.color import Color
import os, os.path, sys
def pdf2jpg(source_file, target_file, dest_width, dest_height):
RESOLUTION = 300
ret = True
try:
with Image(filename=source_file, resolution=(RESOLUTION,RESOLUTION)) as img:
img.background_color = Color('white')
img_width = img.width
ratio = dest_width / img_width
img.resize(dest_width, int(ratio * img.height))
img.format = 'jpeg'
img.save(filename = target_file)
except Exception as e:
ret = False
return ret
if __name__ == "__main__":
source_file = "./02.pdf"
target_file = "./02.jpg"
ret = pdf2jpg(source_file, target_file, 1895, 1080)
Any suggestions for the issue?
I have uploaded the pdf to the url: 02.pdf
You can try...
An easy solution is to change the order of commands: Change the format to jpeg first and then to resize
img.format = 'jpeg'
img.resize(dest_width, int(ratio * img.height))
It is also very easy to open the PDF in the exact size by the resolution tuple, because the resolution can be a float number.
For others who still have this problem I fixed it after googling and trying a couple of hours thanks to this question https://stackoverflow.com/a/40494320/2686243 by using this two lines:
img.background_color = Color("white")
img.alpha_channel = 'remove'
Tried with Wand version 0.4.4
I got the answer by myself. It's because of the alpha_channel case. This pdf includes some transparent background(after i transfomred to png format), and for resize, ImageMagick choose the best resize filter, so black background displayed.
So, after a lot of experiments, I found that just add "img.alpha_channel=False" in "with" statement(before img.save()), that would work properly.
Thanks for VadimR's advise, it is helpful.
来源:https://stackoverflow.com/questions/20439234/python-wand-converts-from-pdf-to-jpg-background-is-incorrect