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POScreenshot of screen subregion using GTK
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copied!<p>I'm trying to take screenshots of only part of the screen using Python under Ubuntu 10.04.</p> <p>Here's my code (assume <code>IMAGE_GRAB</code> is False):</p> <pre><code>def screenshot_roi(regions): if IMAGE_GRAB: return map(ImageGrab.grab, regions) else: w = gtk.gdk.get_default_root_window() sz = w.get_size() pb = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB,False,8,sz[0],sz[1]) src = pb.get_from_drawable(w,w.get_colormap(),0,0,0,0,sz[0],sz[1]) results = [] for roi in regions: if not roi: results.append(None) continue x,y,width,height = roi dst = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB,False,8,width,height) src.copy_area(x,y,width,height,dst,0,0) im = PIL.Image.fromstring("RGB", (width, height), dst.get_pixels()) results.append(im) return results </code></pre> <p>Nothing that fancy here. Captures the entire drawable into a pixel buffer, and then proceeds to crop each pixel buffer before converting it to the required PIL object. </p> <p>This is the mainline:</p> <pre><code>def main(): regions = [(845, 219, 248, 82), (1101, 243, 109, 59), (1213, 245, 66, 57), (1281, 245, 74, 58)] images = screenshot_roi(regions) for i,roi in enumerate(images): if roi: roi.save('%d.png' % i) if __name__ == '__main__': main() </code></pre> <p>The resulting images (all except for the first one) have stride issues, though:</p> <p>1: <img src="https://i.stack.imgur.com/cz9PH.png" alt="enter image description here"> 2: <img src="https://i.stack.imgur.com/BgDJr.png" alt="enter image description here"> 3: <img src="https://i.stack.imgur.com/z91xp.png" alt="enter image description here"> 4: <img src="https://i.stack.imgur.com/qPGeP.png" alt="enter image description here"></p> <p>Now, if I do the cropping in PIL, everything works well:</p> <pre><code>def screenshot_roi(regions): if IMAGE_GRAB: return map(ImageGrab.grab, regions) else: w = gtk.gdk.get_default_root_window() sz = w.get_size() pb = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB,False,8,sz[0],sz[1]) src = pb.get_from_drawable(w,w.get_colormap(),0,0,0,0,sz[0],sz[1]) entire_im = PIL.Image.fromstring("RGB", sz, src.get_pixels()) results = [] for roi in regions: if not roi: results.append(None) continue x,y,width,height = roi crop = entire_im.crop((x,y,x+width,y+height)) crop.load() results.append(crop) return results </code></pre> <p>I don't want to do it this way, thought, because the conversion from GTK to PIL is quite expensive. It's a waste because I'm converting the entire image just to get small sub-regions out of it.</p> <p>Can anyone suggest why the GTK version is having stride errors?</p> <p><em>EDIT</em></p> <p>Working source:</p> <pre><code>x,y,w,h = region win = gtk.gdk.get_default_root_window() pb = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB,False,8,w,h) src = pb.get_from_drawable(win,win.get_colormap(),x,y,0,0,w,h) im = PIL.Image.frombuffer('RGB', (w,h), src.get_pixels(), 'raw', 'RGB', src.get_rowstride(), 1) return im </code></pre>

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