Develop Reference

Image.open() gives a plain white image

I am trying to edit this image:
However, when I run
im = Image.open(filename)
im.show()
it outputs a completely plain white image of the same size. Why is Image.open() not working? How can I fix this? Is there another library I can use to get non-255 pixel values (the correct pixel array)?
Thanks,
Vinny

Image.open actually seems to work fine, as does getpixel, putpixel and save, so you can still load, edit and save the image.
The problem seems to be that the temp file the image is saved in for show is just plain white, so the image viewer shows just a white image. Your original image is 16 bit grayscale, but the temp image is saved as an 8 bit grayscale.
My current theory is that there might actually be a bug in show where a 16 bit grayscale image is just "converted" to 8 bit grayscale by capping all pixel values to 255, resulting in an all-white temp image since all the pixels values in the original are above 30,000.
If you set a pixel to a value below 255 before calling show, that pixel shows correctly. Thus, assuming you want to enhance the contrast in the picture, you can open the picture, map the values to a range from 0 to 255 (e.g. using numpy), and then use show.
from PIL import Image
import numpy as np
arr = np.array(Image.open("Rt5Ov.png"))
arr = (arr - arr.min()) * 255 // (arr.max() - arr.min())
img = Image.fromarray(arr.astype("uint8"))
img.show()
But as said before, since save seems to work as it should, you could also keep the 16 bit grayscale depth and just save the edited image instead of using show.

you can use openCV library for loading images.
import cv2
img = cv2.imread('image file')
plt.show(img)

RGB Values Being Returned by PIL don't match RGB color

I'm attempting to make a reasonably simple code that will be able to read the size of an image and return all the RGB values. I'm using PIL on Python 2.7, and my code goes like this:
import os, sys
from PIL import Image
img = Image.open('C:/image.png')
pixels = img.load()
print(pixels[0, 1])
now this code was actually gotten off of this site as a way to read a gif file. I'm trying to get the code to print out an RGB tuple (in this case (55, 55, 55)) but all it gives me is a small sequence of unrelated numbers, usually containing 34.
I have tried many other examples of code, whether from here or not, but it doesn't seem to work. Is it something wrong with the .png format? Do I need to further code in the rgb part? I'm happy for any help.

My guess is that your image file is using pre-multiplied alpha values. The 8 values you see are pretty close to 55*34/255 (where 34 is the alpha channel value).
PIL uses the mode "RGBa" (with a little a) to indicate when it's using premultiplied alpha. You may be able to tell PIL to covert the to normal "RGBA", where the pixels will have roughly the values you expect:
img = Image.open('C:/image.png').convert("RGBA")
Note that if your image isn't supposed to be partly transparent at all, you may have larger issues going on. We can't help you with that without knowing more about your image.

Python Image Library: clean Downsampling

I've been having trouble trying to get PIL to nicely downsample images. The goal, in this case, is for my website to automagically downsample->cache the original image file whenever a different size is required, thus removing the pain of maintaining multiple versions of the same image. However, I have not had any luck. I've tried:
image.thumbnail((width, height), Image.ANTIALIAS)
image.save(newSource)
and
image.resize((width, height), Image.ANTIALIAS).save(newSource)
and
ImageOps.fit(image, (width, height), Image.ANTIALIAS, (0, 0)).save(newSource)
and all of them seem to perform a nearest-neighbout downsample, rather than averaging over the pixels as it should Hence it turns images like
http://www.techcreation.sg/media/projects//software/Java%20Games/images/Tanks3D%20Full.png
to
http://www.techcreation.sg/media/temp/0x5780b20fe2fd0ed/Tanks3D.png
which isn't very nice. Has anyone else bumped into this issue?

That image is an indexed-color (palette or P mode) image. There are a very limited number of colors to work with and there's not much chance that a pixel from the resized image will be in the palette, since it will need a lot of in-between colors. So it always uses nearest-neighbor mode when resizing; it's really the only way to keep the same palette.
This behavior is the same as in Adobe Photoshop.
You want to convert to RGB mode first and resize it, then go back to palette mode before saving, if desired. (Actually I would just save it in RGB mode, and then turn PNGCrush loose on the folder of resized images.)

This is over a year old, but in case anyone is still looking:
Here is a sample of code that will see if an image is in a palette mode, and make adjustments
import Image # or from PIL import Image
img = Image.open(sourceFile)
if 'P' in img.mode: # check if image is a palette type
img = img.convert("RGB") # convert it to RGB
img = img.resize((w,h),Image.ANTIALIAS) # resize it
img = img.convert("P",dither=Image.NONE, palette=Image.ADAPTIVE)
#convert back to palette
else:
img = img.resize((w,h),Image.ANTIALIAS) # regular resize
img.save(newSourceFile) # save the image to the new source
#img.save(newSourceFile, quality = 95, dpi=(72,72), optimize = True)
# set quality, dpi , and shrink size
By converting the paletted version to RGB, we can resize it with the anti alias. If you want to reconvert it back, then you have to set dithering to NONE, and use an ADAPTIVE palette. If there options aren't included your result (if reconverted to palette) will be grainy. Also you can use the quality option, in the save function, on some image formats to improve the quality even more.

Transparent PNG in PIL turns out not to be transparent

I have been hitting my head against the wall for a while with this, so maybe someone out there can help.
I'm using PIL to open a PNG with transparent background and some random black scribbles, and trying to put it on top of another PNG (with no transparency), then save it to a third file.
It comes out all black at the end, which is irritating, because I didn't tell it to be black.
I've tested this with multiple proposed fixes from other posts. The image opens in RGBA format, and it's still messed up.
Also, this program is supposed to deal with all sorts of file formats, which is why I'm using PIL. Ironic that the first format I tried is all screwy.
Any help would be appreciated. Here's the code:
from PIL import Image
img = Image.open(basefile)
layer = Image.open(layerfile) # this file is the transparent one
print layer.mode # RGBA
img.paste(layer, (xoff, yoff)) # xoff and yoff are 0 in my tests
img.save(outfile)

I think what you want to use is the paste mask argument.
see the docs, (scroll down to paste)
from PIL import Image
img = Image.open(basefile)
layer = Image.open(layerfile) # this file is the transparent one
print layer.mode # RGBA
img.paste(layer, (xoff, yoff), mask=layer)
# the transparancy layer will be used as the mask
img.save(outfile)

fade out in Image module Python

I want to take a BMP or JPG and duplicate it so the new image will darker (or brighrt) what function can I use?
Ariel

You can use ImageEnhance module of PIL:
import Image
import ImageEnhance
image = Image.open(r'c:\temp\20090809210.jpg')
enhancer = ImageEnhance.Brightness(image)
brighter_image = enhancer.enhance(2)
darker_image = enhancer.enhance(0.5)
Look at PIL and ImageEnhance documentation for more details.
Note: I think ImageEnhancer documentation is a bit too terse, and you may need some experimenting within the interactive prompt to get it right.

If you want to do it the hard way i.e. code up a pixel by pixel intensity change. Here is how:
1) Convert from RGB to HSI
2) Increase or decrease the Intensity component
3) Conver back from HSI to RGB
True fade out i.e. alpha channel is not present in the JPG or BMP formats [ RGBA format image in PIL] . You get black to white using the the intensity technique. If you want to use alpha use png or tiff instead.