Blender add-on which provides a function in the VSE to rescale images to their original aspect ratio.

rescale.py

"""
Blender add-on which provides a function in the VSE to rescale images to their
original aspect ratio.

Due to the inclusion of code licensed under GPLv2, this too is licensed under
GPLv2. See: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
"""
import bpy
import os
import struct, imghdr, re

bl_info = {
    "name": "Rescale VSE Images",
    "description": "Adds transform layer to image to rescale to original aspect",
    "author": "J Lawson",
    "version": (1, 0),
    "blender": (2, 77, 0),
    "location": "?",
    "warning": "", # used for warning icon and text in addons panel
    "wiki_url": "",
    "tracker_url": "",
    "support": "COMMUNITY",
    "category": "Sequencer"
    }

def get_image_size(fname):
    """
    Return (width, height) for a given img file content.

    This function is heavily based on a similar funtion in `image.py` from the
    Draco dynamic web content system in python. Draco is available under the
    GPLv2.

    There are a number of similar functions floating around stack exchange, with
    slight changes to functionality. The version included here is based on
    Yantao Xie's version found here:
    https://stackoverflow.com/questions/15800704/
        python-get-image-size-without-loading-image-into-memory
    """
    with open(fname, 'rb') as fhandle:
        head = fhandle.read(32)
        if len(head) != 32:
            return
        if imghdr.what(fname) == 'png':
            check = struct.unpack('>i', head[4:8])[0]
            if check != 0x0d0a1a0a:
                return
            width, height = struct.unpack('>ii', head[16:24])
        elif imghdr.what(fname) == 'gif':
            width, height = struct.unpack('<HH', head[6:10])
        elif imghdr.what(fname) == 'jpeg':
            try:
                fhandle.seek(0) # Read 0xff next
                size = 2
                ftype = 0
                while not 0xc0 <= ftype <= 0xcf:
                    fhandle.seek(size, 1)
                    byte = fhandle.read(1)
                    while ord(byte) == 0xff:
                        byte = fhandle.read(1)
                    ftype = ord(byte)
                    size = struct.unpack('>H', fhandle.read(2))[0] - 2
                # We are at a SOFn block
                fhandle.seek(1, 1)  # Skip `precision' byte.
                height, width = struct.unpack('>HH', fhandle.read(4))
            except Exception: #IGNORE:W0703
                return
        elif imghdr.what(fname) == 'pgm':
            header, width, height, maxval = re.search(
                b"(^P5\s(?:\s*#.*[\r\n])*"
                b"(\d+)\s(?:\s*#.*[\r\n])*"
                b"(\d+)\s(?:\s*#.*[\r\n])*"
                b"(\d+)\s(?:\s*#.*[\r\n]\s)*)", head).groups()
            width = int(width)
            height = int(height)
        elif imghdr.what(fname) == 'bmp':
            _, width, height, depth = re.search(
                b"((\d+)\sx\s"
                b"(\d+)\sx\s"
                b"(\d+))", str).groups()
            width = int(width)
            height = int(height)
        else:
            return
        return width, height

class Rescale_VSE_Image(bpy.types.Operator):
    bl_label = 'Rescale VSE Image'
    bl_idname = 'sequencerextra.rescaleimage'
    bl_description = 'Adds transform layer to image to rescale to original aspect'
    bl_options = {'REGISTER', 'UNDO'}

    @classmethod
    def poll(cls, context):
        """ Ensure that the function is only available for images """
        scn = context.scene
        strip = scn.sequence_editor.active_strip
        if scn and scn.sequence_editor and strip:
            return strip.type in ('IMAGE')
        else:
            return False

    def execute(self, context):
        """
        1. Get the image path
        2. Find the size of the image
        3. Apply a transform to scale the image correctly
        """
        scn = context.scene
        strip = scn.sequence_editor.active_strip
        file = os.path.realpath(bpy.data.filepath + "/.." + strip.directory + strip.name)
        size = get_image_size(file)
        render_setting = scn.render
        render_x = render_setting.resolution_x
        render_y = render_setting.resolution_y
        bpy.ops.sequencer.effect_strip_add(type='TRANSFORM')
        transform = scn.sequence_editor.active_strip
        transform.scale_start_x = render_y/render_x*size[0]/size[1]
        transform.scale_start_y = 1.0
        return {'FINISHED'}

def register():
    bpy.utils.register_class(Rescale_VSE_Image)

def unregister():
    bpy.utils.unregister_class(Rescale_VSE_Image)

rescale_with_pil.py

"""
Blender add-on which provides a function in the VSE to rescale images to their
original aspect ratio.
"""
import bpy
import os
from PIL import Image

bl_info = {
    "name": "Rescale VSE Images",
    "description": "Adds transform layer to image to rescale to original aspect",
    "author": "J Lawson",
    "version": (1, 0),
    "blender": (2, 77, 0),
    "location": "?",
    "warning": "", # used for warning icon and text in addons panel
    "wiki_url": "",
    "tracker_url": "",
    "support": "COMMUNITY",
    "category": "Sequencer"
    }

def get_image_size(fname):
    with Image.open(filename) as img:
        return img.size

class Rescale_VSE_Image(bpy.types.Operator):
    bl_label = 'Rescale VSE Image'
    bl_idname = 'sequencerextra.rescaleimage'
    bl_description = 'Adds transform layer to image to rescale to original aspect'
    bl_options = {'REGISTER', 'UNDO'}

    @classmethod
    def poll(cls, context):
        """ Ensure that the function is only available for images """
        scn = context.scene
        strip = scn.sequence_editor.active_strip
        if scn and scn.sequence_editor and strip:
            return strip.type in ('IMAGE')
        else:
            return False

    def execute(self, context):
        """
        1. Get the image path
        2. Find the size of the image
        3. Apply a transform to scale the image correctly
        """
        scn = context.scene
        strip = scn.sequence_editor.active_strip
        file = os.path.realpath(bpy.data.filepath + "/.." + strip.directory + strip.name)
        size = get_image_size(file)
        render_setting = scn.render
        render_x = render_setting.resolution_x
        render_y = render_setting.resolution_y
        bpy.ops.sequencer.effect_strip_add(type='TRANSFORM')
        transform = scn.sequence_editor.active_strip
        transform.scale_start_x = render_y/render_x*size[0]/size[1]
        transform.scale_start_y = 1.0
        return {'FINISHED'}

def register():
    bpy.utils.register_class(Rescale_VSE_Image)

def unregister():
    bpy.utils.unregister_class(Rescale_VSE_Image)