krita-plugins/image_fitter_docker/image_fitter_docker.py

from krita import DockWidget
from PyQt5.QtWidgets import QWidget, QDialog, QVBoxLayout, QHBoxLayout, QLabel, QButtonGroup, QRadioButton, QComboBox, QPushButton, QCheckBox
from PyQt5.QtCore import QPointF
from math import ceil, floor

DOCKER_TITLE = 'Image Fitter'

class ImageFitter(DockWidget):

    def __init__(self):
        super().__init__()
        self.setWindowTitle(DOCKER_TITLE)
        widget = QWidget()
        layout = QVBoxLayout()
        widget.setLayout(layout)

        layout.addSpacing(10)
        layout.addWidget(QLabel('Fit an image to a rectangle defined by guides.'))

        # Perform scaling or just centering? Many options below should be in the
        # same button group to be disabled en-masse.
        self.scalingCheck = QCheckBox('Scaling')
        self.scalingCheck.setChecked(False)
        layout.addWidget(self.scalingCheck)

        self.aspectCheck = QCheckBox('Keep Aspect Ratio')
        self.aspectCheck.setChecked(True)
        layout.addWidget(self.aspectCheck)

        # Scale image to fit horizontal or vertical rectangle bounds.
        self.matchMode = QComboBox()
        modes = ['Horizontal', 'Vertical']
        self.matchMode.addItems(modes)
        row0 = QHBoxLayout()
        row0.addWidget(QLabel('Scaling Match Mode:'))
        row0.addWidget(self.matchMode)
        layout.addLayout(row0)

        # Scaling strategy.
        # 'Box' is 'Nearest Neighbor'.
        # https://api.kde.org/appscomplete-api/krita-apidocs/libs/image/html/kis__filter__strategy_8h_source.html#l00083
        self.stratInput = QComboBox()
        strategies = ['Box', 'Bicubic', 'Bilinear', 'Lancoz3', 'Bell', 'BSpline', 'Mitchell', 'Hermite']
        self.stratInput.addItems(strategies)
        row1 = QHBoxLayout()
        row1.addWidget(QLabel('Scaling Strategy:'))
        row1.addWidget(self.stratInput)
        layout.addLayout(row1)

        # Button!
        layout.addSpacing(20)
        goButton = QPushButton("Fit")
        goButton.setIcon( Krita.instance().icon('animation_play') )
        layout.addWidget(goButton)

        # Add a stretch to prevent the rest of the content from stretching.
        layout.addStretch()

        # Add widget to the docker.
        self.setWidget(widget)

        # Hook up the action to the button.
        goButton.clicked.connect( self.fitImage )


    # notifies when views are added or removed
    # 'pass' means do not do anything
    def canvasChanged(self, canvas):
        pass


    ##########
    # Slots
    ##########

    # Actually fits the image.
    def fitImage(self, e):

        # Get the current layer.
        doc = Krita.instance().activeDocument()
        layer = doc.activeNode()
        if layer.type() != 'paintlayer':
            dialog = QDialog()
            dialog.setWindowTitle("Paint Layer Required")
            layout = QVBoxLayout()
            layout.addWidget(QLabel('Page slicer only works on paint layers. Please select one.'))
            dialog.setLayout(layout)
            dialog.exec_()
            return

        # Get centres and bounds for the layer and the target rectangle.
        bds = layer.bounds()
        layerCentre = self.getCentre(bds.left(), bds.right() + 1, bds.top(), bds.bottom() + 1)
        tbds = self.getTargetBounds(doc, layerCentre)
        targetCentre = self.getCentre(tbds['left'], tbds['right'], tbds['top'], tbds['bottom'])

        # Handle Scaling. Don't scale if not needed.
        # Repeated scaling does weird things to images.
        if self.scalingCheck.checkState():
            doScaling = False
            targetWidth = tbds['right'] - 1 - tbds['left']
            targetHeight = tbds['bottom'] - 1 - tbds['top']
            layerWidth = bds.right() - bds.left()
            layerHeight = bds.bottom() - bds.top()
            # Deal with aspect ratio. Simply adjust target dimensions.
            if self.aspectCheck.checkState():
                aspectRatio = layerWidth / layerHeight
                mode = self.matchMode.currentIndex()
                if mode == 0: # fit horizontally
                    targetHeight = targetWidth / aspectRatio
                    if layerHeight != targetHeight:
                        doScaling = True
                else: # fit vertically
                    targetWidth = targetHeight * aspectRatio
                    if layerWidth != targetWidth:
                        doScaling = True
            else:
                if layerWidth != targetWidth or layerHeight != targetHeight:
                    doScaling = True
            # Actual scaling.
            if doScaling:
                origin = QPointF(bds.left(), bds.top())
                layer.scaleNode(origin, targetWidth, targetHeight, self.stratInput.currentText())
                # Refresh bounds and centre, which are now changed.
                bds = layer.bounds()
                layerCentre = self.getCentre(bds.left(), bds.right() + 1, bds.top(), bds.bottom() + 1)

        # Round centre coordinates so that odd centres tend towards top-left.
        # Rule that was worked out:
        # - target values are always rounded down.
        # - layer values are rounded up if target is even, down if odd.
        for axis in ['x', 'y']:
            if layerCentre[axis].is_integer() == False and targetCentre[axis].is_integer():
                layerCentre[axis] = ceil(layerCentre[axis])
            else:
                layerCentre[axis] = floor(layerCentre[axis])
            targetCentre[axis] = floor(targetCentre[axis])

        # Reposition.
        # The layer move() function works according to the "actual" position of
        # the layer, which starts off as  the top corner of the image (0, 0).
        # So, instead of giving move() an absolute position, we have to
        # translate the layer's position by applying the difference between the
        # actual layer bounds and the target destination.
        # mid = getLayerCentre(layer) # Bounds may have changed, if scaling.
        diffX = layerCentre['x'] - targetCentre['x']
        diffY = layerCentre['y'] - targetCentre['y']
        layerPos = layer.position()
        layer.move(layerPos.x() - diffX, layerPos.y() - diffY)

        # Refresh the view, or the moved will not be immediately reflected.
        doc.refreshProjection()


    def getCentre(self, left, right, top, bottom):
        return {'x': (left + right)/2, 'y': (top + bottom)/2}


    def getTargetBounds(self, doc, layerCentre):
        # Horizontal guides provide the Vertical y-axis points and vice versa.
        # Also include the edges of the image for the rectangle.
        vPoints = doc.horizontalGuides()
        hPoints = doc.verticalGuides()
        vPoints.insert(0, 0)
        vPoints.append(doc.height())
        hPoints.insert(0, 0)
        hPoints.append(doc.width())

        # Sanitize points. Guide values are floats, and may contain unexpected
        # extra fractional values.
        vPoints = [round(v) for v in vPoints]
        vPoints.sort()
        hPoints = [round(h) for h in hPoints]
        hPoints.sort()

        # Determine the boundaries most relevant to the layer
        bounds = {}
        prevV = 0
        for v in vPoints:
            if v >= layerCentre['y']:
                bounds['top'] = prevV
                bounds['bottom'] = v
                break
            prevV = v

        prevH = 0
        for h in hPoints:
            if h >= layerCentre['x']:
                bounds['left'] = prevH
                bounds['right'] = h
                break
            prevH = h

        return bounds