Overhaul of ScatterPlotItem to improve performance. (API should be mostly unchanged)

Much more efficient at rapid updates.

examples/ScatterPlotSpeedTest.py

@@ -26,7 +26,7 @@ win.show()
 p = ui.plot
 
 data = np.random.normal(size=(50,500), scale=100)
-sizeArray = np.random.random(500) * 20.
+sizeArray = (np.random.random(500) * 20.).astype(int)
 ptr = 0
 lastTime = time()
 fps = None
@@ -49,7 +49,8 @@ def update():
         s = np.clip(dt*3., 0, 1)
         fps = fps * (1-s) + (1.0/dt) * s
     p.setTitle('%0.2f fps' % fps)
-    app.processEvents()  ## force complete redraw for every plot
+    p.repaint()
+    #app.processEvents()  ## force complete redraw for every plot
 timer = QtCore.QTimer()
 timer.timeout.connect(update)
 timer.start(0)

functions.py

@@ -25,6 +25,7 @@ SI_PREFIXES_ASCII = 'yzafpnum kMGTPEZY'
 from .Qt import QtGui, QtCore
 import numpy as np
 import decimal, re
+import ctypes
 
 try:
     import scipy.ndimage
@@ -223,13 +224,15 @@ def mkColor(*args):
     return QtGui.QColor(*args)
 
 
-def mkBrush(*args):
+def mkBrush(*args, **kwds):
     """
     | Convenience function for constructing Brush.
     | This function always constructs a solid brush and accepts the same arguments as :func:`mkColor() <pyqtgraph.mkColor>`
     | Calling mkBrush(None) returns an invisible brush.
     """
-    if len(args) == 1:
+    if 'color' in kwds:
+        color = kwds['color']
+    elif len(args) == 1:
         arg = args[0]
         if arg is None:
             return QtGui.QBrush(QtCore.Qt.NoBrush)
@@ -237,7 +240,7 @@ def mkBrush(*args):
             return QtGui.QBrush(arg)
         else:
             color = arg
-    if len(args) > 1:
+    elif len(args) > 1:
         color = args
     return QtGui.QBrush(mkColor(color))
 
@@ -579,7 +582,10 @@ def solveBilinearTransform(points1, points2):
     
     
     
-    
+def makeRGBA(*args, **kwds):
+    """Equivalent to makeARGB(..., useRGBA=True)"""
+    kwds['useRGBA'] = True
+    return makeARGB(*args, **kwds)
 
 def makeARGB(data, lut=None, levels=None, useRGBA=False): 
     """ 
@@ -605,7 +611,7 @@ def makeARGB(data, lut=None, levels=None, useRGBA=False):
                 Lookup tables can be built using GradientWidget.
         levels - List [min, max]; optionally rescale data before converting through the
                 lookup table.   rescaled = (data-min) * len(lut) / (max-min)
-        useRGBA - If True, the data is returned in RGBA order. The default is 
+        useRGBA - If True, the data is returned in RGBA order (useful for building OpenGL textures). The default is 
                   False, which returns in BGRA order for use with QImage.
                 
     """
@@ -779,29 +785,106 @@ def makeARGB(data, lut=None, levels=None, useRGBA=False):
     return imgData, alpha
     
 
-def makeQImage(imgData, alpha):
+def makeQImage(imgData, alpha=None, copy=True, transpose=True):
-    """Turn an ARGB array into QImage"""
+    """
+    Turn an ARGB array into QImage.
+    By default, the data is copied; changes to the array will not
+    be reflected in the image. The image will be given a 'data' attribute
+    pointing to the array which shares its data to prevent python
+    freeing that memory while the image is in use.
+    
+    =========== ===================================================================
+    Arguments:
+    imgData     Array of data to convert. Must have shape (width, height, 3 or 4) 
+                and dtype=ubyte. The order of values in the 3rd axis must be 
+                (b, g, r, a).
+    alpha       If True, the QImage returned will have format ARGB32. If False,
+                the format will be RGB32. By default, _alpha_ is True if
+                array.shape[2] == 4.
+    copy        If True, the data is copied before converting to QImage.
+                If False, the new QImage points directly to the data in the array.
+                Note that the array must be contiguous for this to work.
+    transpose   If True (the default), the array x/y axes are transposed before 
+                creating the image. Note that Qt expects the axes to be in 
+                (height, width) order whereas pyqtgraph usually prefers the 
+                opposite.
+    =========== ===================================================================    
+    """
     ## create QImage from buffer
     prof = debug.Profiler('functions.makeQImage', disabled=True)
     
+    ## If we didn't explicitly specify alpha, check the array shape.
+    if alpha is None:
+        alpha = (imgData.shape[2] == 4)
+        
+    copied = False
+    if imgData.shape[2] == 3:  ## need to make alpha channel (even if alpha==False; QImage requires 32 bpp)
+        if copy is True:
+            d2 = np.empty(imgData.shape[:2] + (4,), dtype=imgData.dtype)
+            d2[:,:,:3] = imgData
+            d2[:,:,3] = 255
+            imgData = d2
+            copied = True
+        else:
+            raise Exception('Array has only 3 channels; cannot make QImage without copying.')
+    
     if alpha:
         imgFormat = QtGui.QImage.Format_ARGB32
     else:
         imgFormat = QtGui.QImage.Format_RGB32
         
-    imgData = imgData.transpose((1, 0, 2))  ## QImage expects the row/column order to be opposite
+    if transpose:
-    try:
+        imgData = imgData.transpose((1, 0, 2))  ## QImage expects the row/column order to be opposite
-        buf = imgData.data
+    
-    except AttributeError:  ## happens when image data is non-contiguous
+    if not imgData.flags['C_CONTIGUOUS']:
-        imgData = np.ascontiguousarray(imgData)
+        if copy is False:
-        buf = imgData.data
+            extra = ' (try setting transpose=False)' if transpose else ''
+            raise Exception('Array is not contiguous; cannot make QImage without copying.'+extra)
+        imgData = np.ascontiguousarray(imgData)
+        copied = True
+        
+    if copy is True and copied is False:
+        imgData = imgData.copy()
+        
+    addr = ctypes.addressof(ctypes.c_char.from_buffer(imgData, 0))
+    img = QtGui.QImage(addr, imgData.shape[1], imgData.shape[0], imgFormat)
+    img.data = imgData
+    return img
+    #try:
+        #buf = imgData.data
+    #except AttributeError:  ## happens when image data is non-contiguous
+        #buf = imgData.data
+        
+    #prof.mark('1')
+    #qimage = QtGui.QImage(buf, imgData.shape[1], imgData.shape[0], imgFormat)
+    #prof.mark('2')
+    #qimage.data = imgData
+    #prof.finish()
+    #return qimage
+
+def imageToArray(img, copy=False, transpose=True):
+    """
+    Convert a QImage into numpy array. The image must have format RGB32, ARGB32, or ARGB32_Premultiplied.
+    By default, the image is not copied; changes made to the array will appear in the QImage as well (beware: if 
+    the QImage is collected before the array, there may be trouble).
+    The array will have shape (width, height, (b,g,r,a)).
+    """
+    ptr = img.bits()
+    ptr.setsize(img.byteCount())
+    fmt = img.format()
+    if fmt == img.Format_RGB32:
+        arr = np.asarray(ptr).reshape(img.height(), img.width(), 3)
+    elif fmt == img.Format_ARGB32 or fmt == img.Format_ARGB32_Premultiplied:
+        arr = np.asarray(ptr).reshape(img.height(), img.width(), 4)
+    if copy:
+        arr = arr.copy()
+        
+    if transpose:
+        return arr.transpose((1,0,2))
+    else:
+        return arr
+    
     
-    prof.mark('1')
-    qimage = QtGui.QImage(buf, imgData.shape[1], imgData.shape[0], imgFormat)
-    prof.mark('2')
-    qimage.data = imgData
-    prof.finish()
-    return qimage
     
 
 def rescaleData(data, scale, offset):

graphicsItems/PlotDataItem.py

@@ -130,6 +130,8 @@ class PlotDataItem(GraphicsObject):
             'symbolBrush': (50, 50, 150),
             'pxMode': True,
             
+            'pointMode': None,
+            
             'data': None,
         }
         self.setData(*args, **kargs)
@@ -144,22 +146,30 @@ class PlotDataItem(GraphicsObject):
         return QtCore.QRectF()  ## let child items handle this
 
     def setAlpha(self, alpha, auto):
+        if self.opts['alphaHint'] == alpha and self.opts['alphaMode'] == auto:
+            return
         self.opts['alphaHint'] = alpha
         self.opts['alphaMode'] = auto
         self.setOpacity(alpha)
         #self.update()
         
     def setFftMode(self, mode):
+        if self.opts['fftMode'] == mode:
+            return
         self.opts['fftMode'] = mode
         self.xDisp = self.yDisp = None
         self.updateItems()
     
     def setLogMode(self, xMode, yMode):
-        self.opts['logMode'] = (xMode, yMode)
+        if self.opts['logMode'] == [xMode, yMode]:
+            return
+        self.opts['logMode'] = [xMode, yMode]
         self.xDisp = self.yDisp = None
         self.updateItems()
     
     def setPointMode(self, mode):
+        if self.opts['pointMode'] == mode:
+            return
         self.opts['pointMode'] = mode
         self.update()
         
@@ -193,6 +203,8 @@ class PlotDataItem(GraphicsObject):
         
     def setFillBrush(self, *args, **kargs):
         brush = fn.mkBrush(*args, **kargs)
+        if self.opts['fillBrush'] == brush:
+            return
         self.opts['fillBrush'] = brush
         self.updateItems()
         
@@ -200,16 +212,22 @@ class PlotDataItem(GraphicsObject):
         return self.setFillBrush(*args, **kargs)
     
     def setFillLevel(self, level):
+        if self.opts['fillLevel'] == level:
+            return
         self.opts['fillLevel'] = level
         self.updateItems()
 
     def setSymbol(self, symbol):
+        if self.opts['symbol'] == symbol:
+            return
         self.opts['symbol'] = symbol
         #self.scatter.setSymbol(symbol)
         self.updateItems()
         
     def setSymbolPen(self, *args, **kargs):
         pen = fn.mkPen(*args, **kargs)
+        if self.opts['symbolPen'] == pen:
+            return
         self.opts['symbolPen'] = pen
         #self.scatter.setSymbolPen(pen)
         self.updateItems()
@@ -218,21 +236,26 @@ class PlotDataItem(GraphicsObject):
     
     def setSymbolBrush(self, *args, **kargs):
         brush = fn.mkBrush(*args, **kargs)
+        if self.opts['symbolBrush'] == brush:
+            return
         self.opts['symbolBrush'] = brush
         #self.scatter.setSymbolBrush(brush)
         self.updateItems()
     
     
     def setSymbolSize(self, size):
+        if self.opts['symbolSize'] == size:
+            return
         self.opts['symbolSize'] = size
         #self.scatter.setSymbolSize(symbolSize)
         self.updateItems()
 
     def setDownsampling(self, ds):
-        if self.opts['downsample'] != ds:
+        if self.opts['downsample'] == ds:
-            self.opts['downsample'] = ds
+            return
-            self.xDisp = self.yDisp = None
+        self.opts['downsample'] = ds
-            self.updateItems()
+        self.xDisp = self.yDisp = None
+        self.updateItems()
         
     def setData(self, *args, **kargs):
         """
@@ -436,9 +459,12 @@ class PlotDataItem(GraphicsObject):
                         and max)
         =============== =============================================================
         """
+        if frac <= 0.0:
+            raise Exception("Value for parameter 'frac' must be > 0. (got %s)" % str(frac))
+        
         (x, y) = self.getData()
         if x is None or len(x) == 0:
-            return (0, 0)
+            return None
             
         if ax == 0:
             d = x
@@ -450,14 +476,15 @@ class PlotDataItem(GraphicsObject):
         if orthoRange is not None:
             mask = (d2 >= orthoRange[0]) * (d2 <= orthoRange[1])
             d = d[mask]
-            d2 = d2[mask]
+            #d2 = d2[mask]
             
-        if frac >= 1.0:
+        if len(d) > 0:
-            return (np.min(d), np.max(d))
+            if frac >= 1.0:
-        elif frac <= 0.0:
+                return (np.min(d), np.max(d))
-            raise Exception("Value for parameter 'frac' must be > 0. (got %s)" % str(frac))
+            else:
+                return (scipy.stats.scoreatpercentile(d, 50 - (frac * 50)), scipy.stats.scoreatpercentile(d, 50 + (frac * 50)))
         else:
-            return (scipy.stats.scoreatpercentile(d, 50 - (frac * 50)), scipy.stats.scoreatpercentile(d, 50 + (frac * 50)))
+            return None
 
 
     def clear(self):

graphicsItems/ScatterPlotItem.py

@@ -33,22 +33,167 @@ for k, c in coords.items():
     Symbols[k].closeSubpath()
 
     
-def makeSymbolPixmap(size, pen, brush, symbol):
+def drawSymbol(painter, symbol, size, pen, brush):
+    painter.scale(size, size)
+    painter.setPen(pen)
+    painter.setBrush(brush)
+    if isinstance(symbol, basestring):
+        symbol = Symbols[symbol]
+    if np.isscalar(symbol):
+        symbol = Symbols.values()[symbol % len(Symbols)]
+    painter.drawPath(symbol)
+
+    
+def renderSymbol(symbol, size, pen, brush, device=None):
+    """
+    Render a symbol specification to QImage.
+    Symbol may be either a QPainterPath or one of the keys in the Symbols dict.
+    If *device* is None, a new QPixmap will be returned. Otherwise,
+    the symbol will be rendered into the device specified (See QPainter documentation 
+    for more information).
+    """
+    ## see if this pixmap is already cached
+    #global SymbolPixmapCache
+    #key = (symbol, size, fn.colorTuple(pen.color()), pen.width(), pen.style(), fn.colorTuple(brush.color()))
+    #if key in SymbolPixmapCache:
+        #return SymbolPixmapCache[key]
+        
     ## Render a spot with the given parameters to a pixmap
     penPxWidth = max(np.ceil(pen.width()), 1)
-    image = QtGui.QImage(int(size+penPxWidth), int(size+penPxWidth), QtGui.QImage.Format_ARGB32_Premultiplied)
+    image = QtGui.QImage(int(size+penPxWidth), int(size+penPxWidth), QtGui.QImage.Format_ARGB32)
     image.fill(0)
     p = QtGui.QPainter(image)
     p.setRenderHint(p.Antialiasing)
     p.translate(image.width()*0.5, image.height()*0.5)
-    p.scale(size, size)
+    drawSymbol(p, symbol, size, pen, brush)
-    p.setPen(pen)
-    p.setBrush(brush)
-    if isinstance(symbol, basestring):
-        symbol = Symbols[symbol]
-    p.drawPath(symbol)
     p.end()
-    return QtGui.QPixmap(image)
+    return image
+    #pixmap = QtGui.QPixmap(image)
+    #SymbolPixmapCache[key] = pixmap
+    #return pixmap
+
+def makeSymbolPixmap(size, pen, brush, symbol):
+    ## deprecated
+    img = renderSymbol(symbol, size, pen, brush)
+    return QtGui.QPixmap(img)
+    
+class SymbolAtlas:
+    """
+    Used to efficiently construct a single QPixmap containing all rendered symbols
+    for a ScatterPlotItem. This is required for fragment rendering.
+    
+    Use example:
+        atlas = SymbolAtlas()
+        sc1 = atlas.getSymbolCoords('o', 5, QPen(..), QBrush(..))
+        sc2 = atlas.getSymbolCoords('t', 10, QPen(..), QBrush(..))
+        pm = atlas.getAtlas()
+        
+    """
+    class SymbolCoords(list):  ## needed because lists are not allowed in weak references.
+        pass
+    
+    def __init__(self):
+        # symbol key : [x, y, w, h] atlas coordinates
+        # note that the coordinate list will always be the same list object as 
+        # long as the symbol is in the atlas, but the coordinates may
+        # change if the atlas is rebuilt.
+        # weak value; if all external refs to this list disappear, 
+        # the symbol will be forgotten.
+        self.symbolMap = weakref.WeakValueDictionary()
+        
+        self.atlasData = None # numpy array of atlas image
+        self.atlas = None     # atlas as QPixmap
+        self.atlasValid = False
+        
+    def getSymbolCoords(self, opts):
+        """
+        Given a list of spot records, return an object representing the coordinates of that symbol within the atlas
+        """
+        coords = np.empty(len(opts), dtype=object)
+        for i, rec in enumerate(opts):
+            symbol, size, pen, brush = rec['symbol'], rec['size'], rec['pen'], rec['brush']
+            pen = fn.mkPen(pen) if not isinstance(pen, QtGui.QPen) else pen
+            brush = fn.mkBrush(brush) if not isinstance(pen, QtGui.QBrush) else brush
+            key = (symbol, size, fn.colorTuple(pen.color()), pen.width(), pen.style(), fn.colorTuple(brush.color()))
+            if key not in self.symbolMap:
+                newCoords = SymbolAtlas.SymbolCoords()
+                self.symbolMap[key] = newCoords
+                self.atlasValid = False
+                #try:
+                    #self.addToAtlas(key)  ## squeeze this into the atlas if there is room
+                #except:
+                    #self.buildAtlas()  ## otherwise, we need to rebuild
+            
+            coords[i] = self.symbolMap[key]
+        return coords
+        
+    def buildAtlas(self):
+        # get rendered array for all symbols, keep track of avg/max width
+        rendered = {}
+        avgWidth = 0.0
+        maxWidth = 0
+        images = []
+        for key, coords in self.symbolMap.items():
+            if len(coords) == 0:
+                pen = fn.mkPen(color=key[2], width=key[3], style=key[4])
+                brush = fn.mkBrush(color=key[5])
+                img = renderSymbol(key[0], key[1], pen, brush)
+                images.append(img)  ## we only need this to prevent the images being garbage collected immediately
+                arr = fn.imageToArray(img, copy=False, transpose=False)
+            else:
+                (x,y,w,h) = self.symbolMap[key]
+                arr = self.atlasData[x:x+w, y:y+w]
+            rendered[key] = arr
+            w = arr.shape[0]
+            avgWidth += w
+            maxWidth = max(maxWidth, w)
+            
+        nSymbols = len(rendered)
+        if nSymbols > 0:
+            avgWidth /= nSymbols
+            width = max(maxWidth, avgWidth * (nSymbols**0.5))
+        else:
+            avgWidth = 0
+            width = 0
+        
+        # sort symbols by height
+        symbols = sorted(rendered.keys(), key=lambda x: rendered[x].shape[1], reverse=True)
+        
+        self.atlasRows = []
+
+        x = width
+        y = 0
+        rowheight = 0
+        for key in symbols:
+            arr = rendered[key]
+            w,h = arr.shape[:2]
+            if x+w > width:
+                y += rowheight
+                x = 0
+                rowheight = h
+                self.atlasRows.append([y, rowheight, 0])
+            self.symbolMap[key][:] = x, y, w, h
+            x += w
+            self.atlasRows[-1][2] = x
+        height = y + rowheight
+
+        self.atlasData = np.zeros((width, height, 4), dtype=np.ubyte)
+        for key in symbols:
+            x, y, w, h = self.symbolMap[key]
+            self.atlasData[x:x+w, y:y+h] = rendered[key]
+        self.atlas = None
+        self.atlasValid = True
+    
+    def getAtlas(self):
+        if not self.atlasValid:
+            self.buildAtlas()
+        if self.atlas is None:
+            if len(self.atlasData) == 0:
+                return QtGui.QPixmap(0,0)
+            img = fn.makeQImage(self.atlasData, copy=False, transpose=False)
+            self.atlas = QtGui.QPixmap(img)
+        return self.atlas
+        
     
     
     
@@ -79,13 +224,16 @@ class ScatterPlotItem(GraphicsObject):
         """
         prof = debug.Profiler('ScatterPlotItem.__init__', disabled=True)
         GraphicsObject.__init__(self)
-        self.setFlag(self.ItemHasNoContents, True)
+        
-        self.data = np.empty(0, dtype=[('x', float), ('y', float), ('size', float), ('symbol', object), ('pen', object), ('brush', object), ('item', object), ('data', object)])
+        self.picture = None   # QPicture used for rendering when pxmode==False
+        self.fragments = None # fragment specification for pxmode; updated every time the view changes.
+        self.fragmentAtlas = SymbolAtlas()
+        
+        self.data = np.empty(0, dtype=[('x', float), ('y', float), ('size', float), ('symbol', object), ('pen', object), ('brush', object), ('data', object), ('fragCoords', object), ('item', object)])
         self.bounds = [None, None]  ## caches data bounds
         self._maxSpotWidth = 0      ## maximum size of the scale-variant portion of all spots
         self._maxSpotPxWidth = 0    ## maximum size of the scale-invariant portion of all spots
-        self._spotPixmap = None
+        self.opts = {'pxMode': True, 'useCache': True}   ## If useCache is False, symbols are re-drawn on every paint.
-        self.opts = {'pxMode': True}
         
         self.setPen(200,200,200, update=False)
         self.setBrush(100,100,150, update=False)
@@ -96,6 +244,8 @@ class ScatterPlotItem(GraphicsObject):
         prof.mark('setData')
         prof.finish()
         
+        #self.setCacheMode(self.DeviceCoordinateCache)
+        
     def setData(self, *args, **kargs):
         """
         **Ordered Arguments:**
@@ -130,6 +280,7 @@ class ScatterPlotItem(GraphicsObject):
         *identical*            *Deprecated*. This functionality is handled automatically now.
         ====================== ===============================================================================================
         """
+        oldData = self.data  ## this causes cached pixmaps to be preserved while new data is registered.
         self.clear()  ## clear out all old data
         self.addPoints(*args, **kargs)
 
@@ -183,8 +334,8 @@ class ScatterPlotItem(GraphicsObject):
         ## note that np.empty initializes object fields to None and string fields to ''
         
         self.data[:len(oldData)] = oldData
-        for i in range(len(oldData)):
+        #for i in range(len(oldData)):
-            oldData[i]['item']._data = self.data[i]  ## Make sure items have proper reference to new array
+            #oldData[i]['item']._data = self.data[i]  ## Make sure items have proper reference to new array
             
         newData = self.data[len(oldData):]
         newData['size'] = -1  ## indicates to use default size
@@ -217,7 +368,7 @@ class ScatterPlotItem(GraphicsObject):
             newData['y'] = kargs['y']
         
         if 'pxMode' in kargs:
-            self.setPxMode(kargs['pxMode'], update=False)
+            self.setPxMode(kargs['pxMode'])
             
         ## Set any extra parameters provided in keyword arguments
         for k in ['pen', 'brush', 'symbol', 'size']:
@@ -228,12 +379,18 @@ class ScatterPlotItem(GraphicsObject):
         if 'data' in kargs:
             self.setPointData(kargs['data'], dataSet=newData)
         
-        #self.updateSpots()
         self.prepareGeometryChange()
         self.bounds = [None, None]
-        self.generateSpotItems()
+        self.invalidate()
+        self.updateSpots(newData)
         self.sigPlotChanged.emit(self)
         
+    def invalidate(self):
+        ## clear any cached drawing state
+        self.picture = None
+        self.fragments = None
+        self.update()
+        
     def getData(self):
         return self.data['x'], self.data['y']
     
@@ -263,8 +420,8 @@ class ScatterPlotItem(GraphicsObject):
             dataSet['pen'] = pens
         else:
             self.opts['pen'] = fn.mkPen(*args, **kargs)
-            self._spotPixmap = None
         
+        dataSet['fragCoords'] = None
         if update:
             self.updateSpots(dataSet)
         
@@ -285,8 +442,9 @@ class ScatterPlotItem(GraphicsObject):
             dataSet['brush'] = brushes
         else:
             self.opts['brush'] = fn.mkBrush(*args, **kargs)
-            self._spotPixmap = None
+            #self._spotPixmap = None
         
+        dataSet['fragCoords'] = None
         if update:
             self.updateSpots(dataSet)
 
@@ -307,6 +465,7 @@ class ScatterPlotItem(GraphicsObject):
             self.opts['symbol'] = symbol
             self._spotPixmap = None
         
+        dataSet['fragCoords'] = None
         if update:
             self.updateSpots(dataSet)
     
@@ -327,6 +486,7 @@ class ScatterPlotItem(GraphicsObject):
             self.opts['size'] = size
             self._spotPixmap = None
             
+        dataSet['fragCoords'] = None
         if update:
             self.updateSpots(dataSet)
         
@@ -346,34 +506,71 @@ class ScatterPlotItem(GraphicsObject):
         else:
             dataSet['data'] = data
         
-    def setPxMode(self, mode, update=True):
+    def setPxMode(self, mode):
         if self.opts['pxMode'] == mode:
             return
             
         self.opts['pxMode'] = mode
-        self.clearItems()
+        self.invalidate()
-        if update:
-            self.generateSpotItems()
         
     def updateSpots(self, dataSet=None):
         if dataSet is None:
             dataSet = self.data
         self._maxSpotWidth = 0
         self._maxSpotPxWidth = 0
-        for spot in dataSet['item']:
+        invalidate = False
-            spot.updateItem()
         self.measureSpotSizes(dataSet)
+        if self.opts['pxMode']:
+            mask = np.equal(dataSet['fragCoords'], None)
+            if np.any(mask):
+                invalidate = True
+                opts = self.getSpotOpts(dataSet[mask])
+                coords = self.fragmentAtlas.getSymbolCoords(opts)
+                dataSet['fragCoords'][mask] = coords
+                
+            #for rec in dataSet:
+                #if rec['fragCoords'] is None:
+                    #invalidate = True
+                    #rec['fragCoords'] = self.fragmentAtlas.getSymbolCoords(*self.getSpotOpts(rec))
+        if invalidate:
+            self.invalidate()
+
+    def getSpotOpts(self, recs):
+        if recs.ndim == 0:
+            rec = recs
+            symbol = rec['symbol']
+            if symbol is None:
+                symbol = self.opts['symbol']
+            size = rec['size']
+            if size < 0:
+                size = self.opts['size']
+            pen = rec['pen']
+            if pen is None:
+                pen = self.opts['pen']
+            brush = rec['brush']
+            if brush is None:
+                brush = self.opts['brush']
+            return (symbol, size, fn.mkPen(pen), fn.mkBrush(brush))
+        else:
+            recs = recs.copy()
+            recs['symbol'][np.equal(recs['symbol'], None)] = self.opts['symbol']
+            recs['size'][np.equal(recs['size'], -1)] = self.opts['size']
+            recs['pen'][np.equal(recs['pen'], None)] = fn.mkPen(self.opts['pen'])
+            recs['brush'][np.equal(recs['brush'], None)] = fn.mkBrush(self.opts['brush'])
+            return recs
+            
+            
         
     def measureSpotSizes(self, dataSet):
-        for spot in dataSet['item']:
+        for rec in dataSet:
             ## keep track of the maximum spot size and pixel size
+            symbol, size, pen, brush = self.getSpotOpts(rec)
             width = 0
             pxWidth = 0
-            pen = spot.pen()
             if self.opts['pxMode']:
-                pxWidth = spot.size() + pen.width()
+                pxWidth = size + pen.width()
             else:
-                width = spot.size()
+                width = size
                 if pen.isCosmetic():
                     pxWidth += pen.width()
                 else:
@@ -385,19 +582,10 @@ class ScatterPlotItem(GraphicsObject):
     
     def clear(self):
         """Remove all spots from the scatter plot"""
-        self.clearItems()
+        #self.clearItems()
         self.data = np.empty(0, dtype=self.data.dtype)
         self.bounds = [None, None]
-
+        self.invalidate()
-    def clearItems(self):
-        for i in self.data['item']:
-            if i is None:
-                continue
-            i.setParentItem(None)
-            s = i.scene()
-            if s is not None:
-                s.removeItem(i)
-        self.data['item'] = None
 
     def dataBounds(self, ax, frac=1.0, orthoRange=None):
         if frac >= 1.0 and self.bounds[ax] is not None:
@@ -437,27 +625,11 @@ class ScatterPlotItem(GraphicsObject):
             return (scipy.stats.scoreatpercentile(d, 50 - (frac * 50)), scipy.stats.scoreatpercentile(d, 50 + (frac * 50)))
             
 
-
+    #def defaultSpotPixmap(self):
-    
+        ### Return the default spot pixmap
-    
+        #if self._spotPixmap is None:
-    
+            #self._spotPixmap = makeSymbolPixmap(size=self.opts['size'], brush=self.opts['brush'], pen=self.opts['pen'], symbol=self.opts['symbol'])
-    def generateSpotItems(self):
+        #return self._spotPixmap
-        if self.opts['pxMode']:
-            for rec in self.data:
-                if rec['item'] is None:
-                    rec['item'] = PixmapSpotItem(rec, self)
-        else:
-            for rec in self.data:
-                if rec['item'] is None:
-                    rec['item'] = PathSpotItem(rec, self)
-        self.measureSpotSizes(self.data)
-        self.sigPlotChanged.emit(self)
-
-    def defaultSpotPixmap(self):
-        ## Return the default spot pixmap
-        if self._spotPixmap is None:
-            self._spotPixmap = makeSymbolPixmap(size=self.opts['size'], brush=self.opts['brush'], pen=self.opts['pen'], symbol=self.opts['symbol'])
-        return self._spotPixmap
 
     def boundingRect(self):
         (xmn, xmx) = self.dataBounds(ax=0)
@@ -474,15 +646,68 @@ class ScatterPlotItem(GraphicsObject):
         self.prepareGeometryChange()
         GraphicsObject.viewRangeChanged(self)
         self.bounds = [None, None]
+        self.fragments = None
+        
+    def generateFragments(self):
+        tr = self.deviceTransform()
+        if tr is None:
+            return
+        pts = np.empty((2,len(self.data['x'])))
+        pts[0] = self.data['x']
+        pts[1] = self.data['y']
+        pts = fn.transformCoordinates(tr, pts)
+        self.fragments = []
+        for i in xrange(len(self.data)):
+            rec = self.data[i]
+            pos = QtCore.QPointF(pts[0,i], pts[1,i])
+            x,y,w,h = rec['fragCoords']
+            rect = QtCore.QRectF(y, x, h, w)
+            self.fragments.append(QtGui.QPainter.PixmapFragment.create(pos, rect))
             
     def paint(self, p, *args):
-        ## NOTE: self.paint is disabled by this line in __init__:
+        #p.setPen(fn.mkPen('r'))
-        ## self.setFlag(self.ItemHasNoContents, True)
+        #p.drawRect(self.boundingRect())
-        p.setPen(fn.mkPen('r'))
+        if self.opts['pxMode']:
-        p.drawRect(self.boundingRect())
+            atlas = self.fragmentAtlas.getAtlas()
+            #arr = fn.imageToArray(atlas.toImage(), copy=True)
+            #if hasattr(self, 'lastAtlas'):
+                #if np.any(self.lastAtlas != arr):
+                    #print "Atlas changed:", arr
+            #self.lastAtlas = arr
+            
+            if self.fragments is None:
+                self.updateSpots()
+                self.generateFragments()
+                    
+            p.resetTransform()
+            
+            if self.opts['useCache']:
+                p.drawPixmapFragments(self.fragments, atlas)
+            else:
+                for i in range(len(self.data)):
+                    rec = self.data[i]
+                    frag = self.fragments[i]
+                    p.resetTransform()
+                    p.translate(frag.x, frag.y)
+                    drawSymbol(p, *self.getSpotOpts(rec))
+        else:
+            if self.picture is None:
+                self.picture = QtGui.QPicture()
+                p2 = QtGui.QPainter(self.picture)
+                for rec in self.data:
+                    
+                    p2.resetTransform()
+                    p2.translate(rec['x'], rec['y'])
+                    drawSymbol(p2, *self.getSpotOpts(rec))
+                p2.end()
+                
+            self.picture.play(p)
 
         
     def points(self):
+        for rec in self.data:
+            if rec['item'] is None:
+                rec['item'] = SpotItem(rec, self)
         return self.data['item']
         
     def pointsAt(self, pos):
@@ -506,8 +731,8 @@ class ScatterPlotItem(GraphicsObject):
             #else:
                 #print "No hit:", (x, y), (sx, sy)
                 #print "       ", (sx-s2x, sy-s2y), (sx+s2x, sy+s2y)
-        pts.sort(lambda a,b: cmp(b.zValue(), a.zValue()))
+        #pts.sort(lambda a,b: cmp(b.zValue(), a.zValue()))
-        return pts
+        return pts[::-1]
             
 
     def mouseClickEvent(self, ev):
@@ -524,7 +749,7 @@ class ScatterPlotItem(GraphicsObject):
             ev.ignore()
 
 
-class SpotItem(GraphicsItem):
+class SpotItem(object):
     """
     Class referring to individual spots in a scatter plot.
     These can be retrieved by calling ScatterPlotItem.points() or 
@@ -532,14 +757,12 @@ class SpotItem(GraphicsItem):
     """
 
     def __init__(self, data, plot):
-        GraphicsItem.__init__(self, register=False)
+        #GraphicsItem.__init__(self, register=False)
         self._data = data
         self._plot = plot
-        #self._viewBox = None
+        #self.setParentItem(plot)
-        #self._viewWidget = None
+        #self.setPos(QtCore.QPointF(data['x'], data['y']))
-        self.setParentItem(plot)
+        #self.updateItem()
-        self.setPos(QtCore.QPointF(data['x'], data['y']))
-        self.updateItem()
     
     def data(self):
         """Return the user data associated with this spot."""
@@ -553,6 +776,12 @@ class SpotItem(GraphicsItem):
         else:
             return self._data['size']
     
+    def pos(self):
+        return Point(self._data['x'], self._data['y'])
+        
+    def viewPos(self):
+        return self._plot.mapToView(self.pos())
+    
     def setSize(self, size):
         """Set the size of this spot. 
         If the size is set to -1, then the ScatterPlotItem's default size 
@@ -618,37 +847,41 @@ class SpotItem(GraphicsItem):
         """Set the user-data associated with this spot"""
         self._data['data'] = data
 
-
-class PixmapSpotItem(SpotItem, QtGui.QGraphicsPixmapItem):
-    def __init__(self, data, plot):
-        QtGui.QGraphicsPixmapItem.__init__(self)
-        self.setFlags(self.flags() | self.ItemIgnoresTransformations)
-        SpotItem.__init__(self, data, plot)
-    
-    def setPixmap(self, pixmap):
-        QtGui.QGraphicsPixmapItem.setPixmap(self, pixmap)
-        self.setOffset(-pixmap.width()/2.+0.5, -pixmap.height()/2.)
-    
     def updateItem(self):
-        symbolOpts = (self._data['pen'], self._data['brush'], self._data['size'], self._data['symbol'])
+        self._data['fragCoords'] = None
+        self._plot.updateSpots([self._data])
+        self._plot.invalidate()
 
-        ## If all symbol options are default, use default pixmap
+#class PixmapSpotItem(SpotItem, QtGui.QGraphicsPixmapItem):
-        if symbolOpts == (None, None, -1, ''):
+    #def __init__(self, data, plot):
-            pixmap = self._plot.defaultSpotPixmap()
+        #QtGui.QGraphicsPixmapItem.__init__(self)
-        else:
+        #self.setFlags(self.flags() | self.ItemIgnoresTransformations)
-            pixmap = makeSymbolPixmap(size=self.size(), pen=self.pen(), brush=self.brush(), symbol=self.symbol())
+        #SpotItem.__init__(self, data, plot)
-        self.setPixmap(pixmap)
+    
+    #def setPixmap(self, pixmap):
+        #QtGui.QGraphicsPixmapItem.setPixmap(self, pixmap)
+        #self.setOffset(-pixmap.width()/2.+0.5, -pixmap.height()/2.)
+    
+    #def updateItem(self):
+        #symbolOpts = (self._data['pen'], self._data['brush'], self._data['size'], self._data['symbol'])
+        
+        ### If all symbol options are default, use default pixmap
+        #if symbolOpts == (None, None, -1, ''):
+            #pixmap = self._plot.defaultSpotPixmap()
+        #else:
+            #pixmap = makeSymbolPixmap(size=self.size(), pen=self.pen(), brush=self.brush(), symbol=self.symbol())
+        #self.setPixmap(pixmap)
 
 
-class PathSpotItem(SpotItem, QtGui.QGraphicsPathItem):
+#class PathSpotItem(SpotItem, QtGui.QGraphicsPathItem):
-    def __init__(self, data, plot):
+    #def __init__(self, data, plot):
-        QtGui.QGraphicsPathItem.__init__(self)
+        #QtGui.QGraphicsPathItem.__init__(self)
-        SpotItem.__init__(self, data, plot)
+        #SpotItem.__init__(self, data, plot)
 
-    def updateItem(self):
+    #def updateItem(self):
-        QtGui.QGraphicsPathItem.setPath(self, Symbols[self.symbol()])
+        #QtGui.QGraphicsPathItem.setPath(self, Symbols[self.symbol()])
-        QtGui.QGraphicsPathItem.setPen(self, self.pen())
+        #QtGui.QGraphicsPathItem.setPen(self, self.pen())
-        QtGui.QGraphicsPathItem.setBrush(self, self.brush())
+        #QtGui.QGraphicsPathItem.setBrush(self, self.brush())
-        size = self.size()
+        #size = self.size()
-        self.resetTransform()
+        #self.resetTransform()
-        self.scale(size, size)
+        #self.scale(size, size)