DUV_UVTransfer.py

import bpy
import bmesh
from bpy.types import Menu
from bpy.props import EnumProperty, BoolProperty

class DREAMUV_OT_uv_transfer(bpy.types.Operator):
    """Transfer to selection"""
    bl_idname = "view3d.dreamuv_uvtransfer"
    bl_label = "UV Transfer"
    bl_options = {"UNDO"}

    def execute(self, context):  
        
        bpy.ops.uv.select_split()
 
        obj = bpy.context.view_layer.objects.active
        bm = bmesh.from_edit_mesh(obj.data)
        uv_layer = bm.loops.layers.uv.verify()

        faces = list()

        xmin,xmax,ymin,ymax=0,0,0,0

        selected_uv_loops = list()

        for i,face in enumerate(bm.faces):
            if face.select:
                for o,vert in enumerate(face.loops):
                    if vert[bm.loops.layers.uv.active].select:
                        selected_uv_loops.append(vert)

        #if nothing is selected, match UV selection to mesh selection

        if len(selected_uv_loops) == 0:
            for i,face in enumerate(bm.faces):
                if face.select:
                    selected_uv_loops.extend(face.loops)

        first = True
        for vert in selected_uv_loops:
            if first:
                xmin=vert[bm.loops.layers.uv.active].uv.x
                xmax=vert[bm.loops.layers.uv.active].uv.x
                ymin=vert[bm.loops.layers.uv.active].uv.y
                ymax=vert[bm.loops.layers.uv.active].uv.y
                first=False
            else:
                if vert[bm.loops.layers.uv.active].uv.x < xmin:
                    xmin=vert[bm.loops.layers.uv.active].uv.x
                elif vert[bm.loops.layers.uv.active].uv.x > xmax:
                    xmax=vert[bm.loops.layers.uv.active].uv.x
                if vert[bm.loops.layers.uv.active].uv.y < ymin:
                    ymin=vert[bm.loops.layers.uv.active].uv.y
                elif vert[bm.loops.layers.uv.active].uv.y > ymax:
                    ymax=vert[bm.loops.layers.uv.active].uv.y


        aspect = (xmax-xmin)/(ymax-ymin)
        aspecttarget = (context.scene.uvtransferxmax-context.scene.uvtransferxmin)/(context.scene.uvtransferymax-context.scene.uvtransferymin)
        print("aspects")
        print(aspect)
        print(aspecttarget)
        

        #move to 0,1

        for vert in selected_uv_loops:
            vert[bm.loops.layers.uv.active].uv.x -= xmin
            vert[bm.loops.layers.uv.active].uv.y -= ymin
            vert[bm.loops.layers.uv.active].uv.x /= (xmax-xmin)
            vert[bm.loops.layers.uv.active].uv.y /= (ymax-ymin)

        xmin2 = .5
        ymin2 = .5

        xmax2 = 1
        ymax2 = 1

        #move to new rect

        for vert in selected_uv_loops:
            vert[bm.loops.layers.uv.active].uv.x = (vert[bm.loops.layers.uv.active].uv.x * (context.scene.uvtransferxmax-context.scene.uvtransferxmin)) + context.scene.uvtransferxmin
            vert[bm.loops.layers.uv.active].uv.y = (vert[bm.loops.layers.uv.active].uv.y * (context.scene.uvtransferymax-context.scene.uvtransferymin)) + context.scene.uvtransferymin

                
        bmesh.update_edit_mesh(obj.data)

        #cycle if needed:
        if (aspect >= 1 and aspecttarget < 1) or (aspect <= 1 and aspecttarget > 1):
            bpy.ops.view3d.dreamuv_uvcycle()
        return {'FINISHED'}

class DREAMUV_OT_uv_transfer_grab(bpy.types.Operator):
    """UV Transfer Grab"""
    bl_idname = "view3d.dreamuv_uvtransfergrab"
    bl_label = "UV Transfer Grab"
    bl_options = {"UNDO"}

    def execute(self, context):
        bpy.ops.uv.select_split()
 
        obj = bpy.context.view_layer.objects.active
        bm = bmesh.from_edit_mesh(obj.data)
        uv_layer = bm.loops.layers.uv.verify()

        faces = list()

        xmin,xmax,ymin,ymax=0,0,0,0

        

        selected_uv_loops = list()

        for i,face in enumerate(bm.faces):
            if face.select:
                for o,vert in enumerate(face.loops):
                    if vert[bm.loops.layers.uv.active].select:
                        selected_uv_loops.append(vert)

        #if nothing is selected, match UV selection to mesh selection

        if len(selected_uv_loops) == 0:
            for i,face in enumerate(bm.faces):
                if face.select:
                    selected_uv_loops.extend(face.loops)

        first = True
        for vert in selected_uv_loops:
            if first:
                xmin=vert[bm.loops.layers.uv.active].uv.x
                xmax=vert[bm.loops.layers.uv.active].uv.x
                ymin=vert[bm.loops.layers.uv.active].uv.y
                ymax=vert[bm.loops.layers.uv.active].uv.y
                first=False
            else:
                if vert[bm.loops.layers.uv.active].uv.x < xmin:
                    xmin=vert[bm.loops.layers.uv.active].uv.x
                elif vert[bm.loops.layers.uv.active].uv.x > xmax:
                    xmax=vert[bm.loops.layers.uv.active].uv.x
                if vert[bm.loops.layers.uv.active].uv.y < ymin:
                    ymin=vert[bm.loops.layers.uv.active].uv.y
                elif vert[bm.loops.layers.uv.active].uv.y > ymax:
                    ymax=vert[bm.loops.layers.uv.active].uv.y


        context.scene.uvtransferxmax = xmax
        context.scene.uvtransferxmin = xmin
        context.scene.uvtransferymax = ymax
        context.scene.uvtransferymin = ymin

        return {'FINISHED'}