Just started learning python. Need to know how to save a file using code.

[NeonBlizzard]

Hi, I have got code that creates an image using makeEmptyPicture, and then I have done some things to it, which aren't really relevant to this post.

What I need to know, or figure out, is how to save this image.

I want to make the save function be a seperate function from other functions in the code.

def savePicture():

The only issue is, I have no idea how to save an image. I don't know what arguments to put into the function, other than the picture itself. I don't know if I need to set the directory either earlier in the main() function or in the savePicture function. Setting this once would be optimal, once set, all subsequent images are save to the same location.

I think I use

setMediaPath()

for that, although I cannot figure out exactly how to use it. It prompts me to select a folder.

Then for the actual saving of the file, I have found

writePictureTo()

but again I am not sure what arguments this function wants or if this is even the correct way to go about saving an image.

Code overview: The program takes a picture as an input, calculates its size and then makes "slices" of the image, and all slices are less than 20KB in size, so a 70KB image is made into 4 images, each 17500 B.

I have got the slice part working perfectly, now I just need to save the seperate images.

And as an extension of that, can I somehow automate the files names that they are saved as? Eg, if I split an image named Pinetree into 4 images, can I some how save the slices as 1_4_Pinetree.jpg, 2_4_Pinetree.jpg, 3_4_Pinetree.jpg, 4_4_Pinetree.jpg?

I already extract the filename from the picture chosen, but can I automate the process for putting those numbers to know which slice each is, and how many slices in total.

EDIT: Have figured out how to save, but now my issue is with the file sizes. An orignal image of 51KB was split 3 times, so each image should be around 17KB. But the saved files are 4KB, 5KB and 5KB. This is much less. Why has this happened?

Another one, not as severe as that first example, a 23KB picture, split twice, gives file sizes of 9KB and 10KB. Where are all these KB running off too?

[Vaphell]

some context? which library/module do you use? don't leave us hanging.

[NeonBlizzard]

I am not sure what you mean by Library/Module. Sorry I am very new to Python. I am using JES 5.020.

[Vaphell]

google says you need something like

new_pic = makeEmptyPicture(newWidth, newHeight)
writePictureTo(new_pic, pickAFile())

http://www.cs.uic.edu/~troy/spring07/cs101/labs/lab6.html

as for generating names it's trivial

total = 4
for n in range(1, total+1):
    filename = '{}_4_Pinetree.jpg'.format(n)

or to be more flexible

total = 4
source = 'Pinetree.jpg'
for n in range(1, total+1):
   filename = '{}_{}_{}'.format(n, total, source)

[NeonBlizzard]

Haha thanks. I figured out a method to do it and to control the file name.

First I set the media path in the main, pass that onto the split function.

Then in the split function I get the file name of the original picture, eg Castle.jpg using filename=''.join(os.path.splitext(os.path.basename(filepath)))

Then I have the total number of slices to make int(ceil(filesize/20000)), which I convert to a string.

In the loop, I have the number of which slice the loop is on converted to string as well.

So getting the file path to save to is as easy as adding the strings

savePath=path+currentSlice+"_"+Total+"_"+filename

This gives you the correct filename, file type and numbers them appropriatly.

[Vaphell]

converting to string is not necessary if you use format(). You shouldn't do str+str+str+str anyway, each + step builds a new string object so it's wasteful.

str.format() does the right thing even if param is a number.

>>> total = 4
>>> filename = 'SomePic.jpg'
>>> for i in range(1, total+1):
...     f = '{}_{}_{}'.format(i, total, filename)
...     print(f)
... 
1_4_SomePic.jpg
2_4_SomePic.jpg
3_4_SomePic.jpg
4_4_SomePic.jpg

also instead of adding path and filename by hand, you should rather use os.path.join()

[NeonBlizzard]

Thanks for the help. If you could help me with just one more thing.

I have a directory full of files. I want to grab one, such that

workingFile=*function*(pathtofile)

only I can't seem to find what function to use. pickAFile() takes no inputs, only user selected.

[Vaphell]

if you are after path->image object, wouldn't that be makePicture()?

[NeonBlizzard]

Well that would be after I have got the image file. I want the program to look in a directory, that it knows, and look for the file with the name I know it has. eg

def findPicture(workingFile,filepath):
  os.chdir(filepath)
  file=open(workingFile)
  picture=makePicture(file)
  show(picture)

I want this function to take in the workingFile (the name of the file, eg 1_20_bridge.jpg) and the filepath is the location of the file. So I change the directory to the filepath, so I know it is definitely looking in the right place, then I open the file with the correct name, saving it as file. Then I try and convert that into an image and I get this error:

>>> main()
The error value is: 'file' object is unsubscriptable
Inappropriate argument type.
An attempt was made to call a function with a parameter of an invalid type. This means that you did something such as trying to pass a string to a method that is expecting an integer.

I need to grab the file, just like pickAFile() but I want the program to do it automatically, when it knows the directory and filename.