如何在python中的文件夹中使用PIL调整图像大小

Question

I am using PIL/Python to resize the images in a folder . After resizing the images I want to save them again in the same folder with the same name but I am having error cannot write mode RGBA as JPEG

there are multiple formats of images inside the folder

this is the code which is used to resize the images

path = "data/images/"
dirs = os.listdir( path )

def resize():
    for item in dirs:
        if os.path.isfile(path+item):
            im = Image.open(path+item)
            f, e = os.path.splitext(path+item)
            imResize = im.resize((200,200), Image.ANTIALIAS)
            imResize.save(f, 'JPEG', quality=90)

resize()

this is the error I am having

cannot write mode RGBA as JPEG

Answer 1

Try:-

f = "apple.png"
im = Image.open(path+item)
im = im.convert("RGB") 
imResize = im.resize((200,200), Image.ANTIALIAS)
imResize.save(f, quality=90)

We removed the alpha channel from the image, and converted the color space to RGB only. As most file formats support a image with RGB color space, I don't think errors will still continue to exist.

Don't explicitly define the output format of all input images as .jpeg , rather let PIL determine it by looking at the file's extension.

PS:- Don't use this method if transparency of the image is taken into account(alpha channel), as this method will get rid of the alpha channel of the image.

Answer 2

To resize images I always have used .thumbnail . It's easy to use and it simply works. To keep the data of the colors and the alpha, the solution brought by Vasu Deo.S works well and it's the one I am using on my script.

You need to save your images in .png instead of .jpeg to avoid the error of the alpha channel.

So here's your code edited that actually works.

path = "data/images/"
dirs = os.listdir( path )

def resizeImages():
    for item in dirs:
        if os.path.isfile(path+item):
            im = Image.open(path+item)
            im = im.convert('RGBA')

            size = 200, 200

            imResize.thumbnail(size)

            f, e = os.path.splitext(path+item)
            imResize.save(f+'.png')

Note that this, will need to be saved as .png . If you want to save as a .jpeg image, you must get rid of the alpha channel using this:

path = "data/images/"
dirs = os.listdir( path )

def resizeImages():
    for item in dirs:
        if os.path.isfile(path+item):
            im = Image.open(path+item)
            im = im.convert('RGBA')

            data = np.array(im)
            red, green, blue, alpha = data.T

            alpha_areas = (red == 0) & (blue == 0) & (green == 0) & (alpha == 0) # set alpha to 0
            data[..., :-1][alpha_areas.T] = (255,255,255)
            im = Image.fromarray(data)

            size = 200, 200

            imResize = im.thumbnail(size)

            f, e = os.path.splitext(path+item)
            imResize.save(f+'.png')