django-photologue: How to scale image to box and fill background

Question

I´m using django-photologue (with 1pinax) and want to scale images to a box (100px x 100px). Portrait images should be scaled to height 100px and the width should be filled with a color.

Answer 1

You can use PIL with a transformation matrix. For example, the following function resize and crop in a single operation. Personally I prefer to crop rather than fill it with a color, but you can adjust it to your needs.

def resize_and_crop(im, mask_width=1000, mask_height=1000):
    width, height = im.size
    aspect = 1.0*width/height
    mask_aspect = 1.0*mask_width/mask_height
    if width != mask_width or height != mask_height:
        if aspect > mask_aspect:
            ratio = 1.0*height/mask_height
            imt = im.transform((mask_width, mask_height), 
                                Image.AFFINE, 
                               (ratio, 0, (width-mask_width*ratio)/2, 0, ratio, 0),
                               Image.CUBIC)
        else:
            ratio = 1.0*width/mask_width
            imt = im.transform((mask_width, mask_height), 
                               Image.AFFINE, 
                               (ratio, 0, 0, 0, ratio, (height-mask_height*ratio)/2),
                               Image.CUBIC)
    else:
        imt = im
    return imt