I've implemented a screenshot function of NSView, UIView and GLKView.

Frank.xcodeproj/project.pbxproj

@@ -74,6 +74,12 @@
 		4C1DD76D12BADFE100E10B8C /* OrientationCommand.h in Headers */ = {isa = PBXBuildFile; fileRef = 4C1DD76912BADFE100E10B8C /* OrientationCommand.h */; };
 		4C1DD76E12BADFE100E10B8C /* AppCommand.m in Sources */ = {isa = PBXBuildFile; fileRef = 4C1DD76A12BADFE100E10B8C /* AppCommand.m */; };
 		4C1DD76F12BADFE100E10B8C /* AppCommand.h in Headers */ = {isa = PBXBuildFile; fileRef = 4C1DD76B12BADFE100E10B8C /* AppCommand.h */; };
+		520C60F617858EB9003D2535 /* NSView+Frank.m in Sources */ = {isa = PBXBuildFile; fileRef = 520C60F417858EB9003D2535 /* NSView+Frank.m */; };
+		520C60F917858FD7003D2535 /* NSView+Frank.h in Headers */ = {isa = PBXBuildFile; fileRef = 520C60F817858FD7003D2535 /* NSView+Frank.h */; };
+		520C60FB1785901D003D2535 /* UIView+Frank.h in Headers */ = {isa = PBXBuildFile; fileRef = 520C60FA1785901D003D2535 /* UIView+Frank.h */; };
+		52B355C717844C2700060740 /* GLKView+ImageCapture.h in Headers */ = {isa = PBXBuildFile; fileRef = 52B355C517844C2700060740 /* GLKView+ImageCapture.h */; };
+		52B355C817844C2700060740 /* GLKView+ImageCapture.m in Sources */ = {isa = PBXBuildFile; fileRef = 52B355C617844C2700060740 /* GLKView+ImageCapture.m */; };
+		52B355CB17844DA400060740 /* GLKit.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 52B355CA17844DA400060740 /* GLKit.framework */; };
 		65DBDD7416A89CCA007D3D43 /* GCDAsyncSocket.m in Sources */ = {isa = PBXBuildFile; fileRef = AB7947C115C4418700052B74 /* GCDAsyncSocket.m */; };
 		65DBDD8D16A89CCA007D3D43 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = AACBBE490F95108600F1A2B1 /* Foundation.framework */; };
 		65DBDDA816A89CDC007D3D43 /* DDAbstractDatabaseLogger.m in Sources */ = {isa = PBXBuildFile; fileRef = ABA9E4BB15C81E7900112290 /* DDAbstractDatabaseLogger.m */; };
@@ -316,6 +322,12 @@
 		4C1DD76912BADFE100E10B8C /* OrientationCommand.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = OrientationCommand.h; sourceTree = "<group>"; };
 		4C1DD76A12BADFE100E10B8C /* AppCommand.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = AppCommand.m; sourceTree = "<group>"; };
 		4C1DD76B12BADFE100E10B8C /* AppCommand.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = AppCommand.h; sourceTree = "<group>"; };
+		520C60F417858EB9003D2535 /* NSView+Frank.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "NSView+Frank.m"; sourceTree = "<group>"; };
+		520C60F817858FD7003D2535 /* NSView+Frank.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSView+Frank.h"; sourceTree = "<group>"; };
+		520C60FA1785901D003D2535 /* UIView+Frank.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "UIView+Frank.h"; sourceTree = "<group>"; };
+		52B355C517844C2700060740 /* GLKView+ImageCapture.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "GLKView+ImageCapture.h"; sourceTree = "<group>"; };
+		52B355C617844C2700060740 /* GLKView+ImageCapture.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "GLKView+ImageCapture.m"; sourceTree = "<group>"; };
+		52B355CA17844DA400060740 /* GLKit.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = GLKit.framework; path = System/Library/Frameworks/GLKit.framework; sourceTree = SDKROOT; };
 		65DBDD9216A89CCA007D3D43 /* libCocoaAsyncSocket.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libCocoaAsyncSocket.a; sourceTree = BUILT_PRODUCTS_DIR; };
 		65DBDDB516A89CDC007D3D43 /* libCocoaLumberjack.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libCocoaLumberjack.a; sourceTree = BUILT_PRODUCTS_DIR; };
 		65DBDDDA16A89E5B007D3D43 /* libCocoaAsyncSocketMac.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libCocoaAsyncSocketMac.a; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -489,6 +501,7 @@
 				AACBBE4A0F95108600F1A2B1 /* Foundation.framework in Frameworks */,
 				D629938011AB2DF300CE0FB0 /* UIKit.framework in Frameworks */,
 				00E864C5161D708B00E01209 /* MapKit.framework in Frameworks */,
+				52B355CB17844DA400060740 /* GLKit.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -517,6 +530,7 @@
 				305CA7A31642063E00C4ACE5 /* Foundation.framework */,
 				C18A5F20160D572300DC25F6 /* libPublicAutomation.a */,
 				00E864C4161D708B00E01209 /* MapKit.framework */,
+				52B355CA17844DA400060740 /* GLKit.framework */,
 				08FB77AEFE84172EC02AAC07 /* src */,
 				D629926711AB2CF700CE0FB0 /* lib */,
 				0867D69AFE84028FC02AAC07 /* Frameworks */,
@@ -754,9 +768,12 @@
 			children = (
 				C9605E681606BFAE00170F88 /* UIImage+Frank.h */,
 				C9605E691606BFAE00170F88 /* UIImage+Frank.m */,
+				520C60FA1785901D003D2535 /* UIView+Frank.h */,
 				D6A1D27E15A8D05E00EC056C /* UIView+Frank.m */,
 				C18A5EF3160D4AD300DC25F6 /* UIView+ImageCapture.h */,
 				C18A5EF4160D4AD300DC25F6 /* UIView+ImageCapture.m */,
+				52B355C517844C2700060740 /* GLKView+ImageCapture.h */,
+				52B355C617844C2700060740 /* GLKView+ImageCapture.m */,
 				C9605E661606BF8E00170F88 /* UIView+MapKitWorkaround.m */,
 				C18A5F1D160D547A00DC25F6 /* UIView+PublicAutomation.m */,
 				387BFA7C17036DDA007B9F17 /* UISlider+PublicAutomation.m */,
@@ -767,6 +784,8 @@
 				302B803F1646DE02000F9861 /* NSImage+Frank.h */,
 				302B80401646DE02000F9861 /* NSImage+Frank.m */,
 				303A751116702D3D00B93673 /* NSObject+FrankAutomation.m */,
+				520C60F817858FD7003D2535 /* NSView+Frank.h */,
+				520C60F417858EB9003D2535 /* NSView+Frank.m */,
 				30412D2E165333E300719CD2 /* NSView+FrankImageCapture.h */,
 				30412D2F165333E300719CD2 /* NSView+FrankImageCapture.m */,
 			);
@@ -822,6 +841,7 @@
 				C189EF1F16BB5A8100F8236D /* VersionCommand.h in Headers */,
 				303CFCE516C80B830004BD05 /* DeviceCommand.h in Headers */,
 				30E82E3317128AB500E5BC7C /* ResolutionCommand.h in Headers */,
+				520C60F917858FD7003D2535 /* NSView+Frank.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -865,6 +885,8 @@
 				303CFCE416C80B830004BD05 /* DeviceCommand.h in Headers */,
 				30E82E3217128AB500E5BC7C /* ResolutionCommand.h in Headers */,
 				0626BFAE174300240020B33B /* DumpCommandRoute.h in Headers */,
+				52B355C717844C2700060740 /* GLKView+ImageCapture.h in Headers */,
+				520C60FB1785901D003D2535 /* UIView+Frank.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -1109,6 +1131,7 @@
 				C189EF2116BB5A8100F8236D /* VersionCommand.m in Sources */,
 				303CFCE716C80B830004BD05 /* DeviceCommand.m in Sources */,
 				30E82E3517128AB500E5BC7C /* ResolutionCommand.m in Sources */,
+				520C60F617858EB9003D2535 /* NSView+Frank.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -1238,6 +1261,7 @@
 				30E82E3417128AB500E5BC7C /* ResolutionCommand.m in Sources */,
 				387BFA7D17036DDA007B9F17 /* UISlider+PublicAutomation.m in Sources */,
 				0626BFAF174300240020B33B /* DumpCommandRoute.m in Sources */,
+				52B355C817844C2700060740 /* GLKView+ImageCapture.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

gem/frank-skeleton/frankify.xcconfig.tt

@@ -1,6 +1,6 @@
 INSTALL_PATH = /./
 
-FRANK_CORE_LDFLAGS = -all_load -ObjC -framework CFNetwork -framework Security -lShelley -lFrank <%= @libs.map { |lib| "-l#{lib}" }.join(' ') %>
+FRANK_CORE_LDFLAGS = -all_load -ObjC -framework CFNetwork -framework Security -framework GLKit -lShelley -lFrank <%= @libs.map { |lib| "-l#{lib}" }.join(' ') %>
 FRANK_CORE_MAC_LDFLAGS = -all_load -ObjC -framework CFNetwork -framework Security -lShelleyMac -lFrankMac <%= @libsMac.map { |lib| "-l#{lib}" }.join(' ') %>
 
 FRANK_CORE_GCC_PREPROCESSOR_DEFINITIONS_NOT_USED_IN_PRECOMPS = FRANKIFIED

gem/lib/frank-cucumber/frank_helper.rb

@@ -1,4 +1,5 @@
 require 'json'
+require 'base64'
 require 'frank-cucumber/gateway'
 require 'frank-cucumber/host_scripting'
 require 'frank-cucumber/wait_helper'
@@ -88,6 +89,25 @@ def touch( selector )
     touch_successes
   end
 
+  # grab screenshots of all views matching the specified selector.
+  # @param [String] selector a view selector.
+  # @return [Array<PNG>] an array of PNG-image binary.
+  # @raise an expection if no views matched the selector
+  # @raise an expection if no views which matched the selector could be capture
+  def capture( selector )
+    view_uids = frankly_map( selector, 'FEX_UID' )
+    raise "could not find anything matching [#{selector}] to capture" if view_uids.empty?
+    raise "some views could not be capture image" if view_uids.include?(nil)
+
+    frank_server.send_get( 'screenshot/snapshot-all-views' )
+    screenshots = view_uids.map{|uid|
+      path = "screenshot/view-snapshot/#{uid}"
+      frank_server.send_get( path )
+    }
+    raise "some views failed to capture image" if screenshots.include?(nil)
+    screenshots
+  end
+
   # Fill in text in a text field.
   #
   # @param [String] the placeholder text for the desired text field

src/GLKView+ImageCapture.h

@@ -0,0 +1,14 @@
+//
+//  GLKView+ImageCapture.h
+//  Frank
+//
+//  Created by Toshiyuki Suzumura on 2013/07/03.
+//
+
+#import <GLKit/GLKit.h>
+
+@interface GLKView (ImageCapture)
+
+- (UIImage *)captureImage;
+
+@end

src/GLKView+ImageCapture.m

@@ -0,0 +1,16 @@
+//
+//  GLKView+ImageCapture.m
+//  Frank
+//
+//  Created by Toshiyuki Suzumura on 2013/07/03.
+//
+
+#import "GLKView+ImageCapture.h"
+
+@implementation GLKView (ImageCapture)
+
+- (UIImage*)captureImage {
+    return [self snapshot];
+}
+
+@end

src/ImageCaptureRoute.m

@@ -14,9 +14,11 @@
 
 #if TARGET_OS_IPHONE
 #import "UIImage+Frank.h"
+#import "UIView+Frank.h"
 #import "UIView+ImageCapture.h"
 #else
 #import "NSImage+Frank.h"
+#import "NSView+Frank.h"
 #import "NSView+FrankImageCapture.h"
 #endif
 #import "FranklyProtocolHelper.h"
@@ -49,15 +51,15 @@ - (void) snapshotView:(UIView *)view{
     UIImage *image = [view captureImage];
     NSData *imgData = UIImagePNGRepresentation(image);
 
-    NSString *viewUID = [NSString stringWithFormat:@"%i",(int)view];
+    NSString *viewUID = [view FEX_UID];
     [imgData writeToFile:[self pathForSnapshotOfViewWithUID:viewUID] atomically:NO];
 }
 #else
 - (void) snapshotView:(NSView *)view{
     NSImage *image = [view captureImage];
     NSData *imgData = [[[image representations] objectAtIndex:0] representationUsingType:NSPNGFileType properties:nil];
 
-    NSString *viewUID = [NSString stringWithFormat:@"%lu",(uintptr_t)view];
+    NSString *viewUID = [view FEX_UID];
     [imgData writeToFile:[self pathForSnapshotOfViewWithUID:viewUID] atomically:NO];
 }
 #endif

src/NSView+Frank.h

@@ -0,0 +1,14 @@
+//
+//  NSView+Frank.h
+//  Frank
+//
+//  Created by Toshiyuki Suzumura on 2013/07/04.
+//
+
+#import <Cocoa/Cocoa.h>
+
+@interface NSView (Frank)
+
+- (NSString *) FEX_UID;
+
+@end

src/NSView+Frank.m

@@ -0,0 +1,16 @@
+//
+//  NSView+Frank.m
+//  Frank
+//
+//  Created by Toshiyuki Suzumura on 2013/07/04.
+//
+
+#import "NSView+Frank.h"
+
+@implementation NSView (Frank)
+
+- (NSString *) FEX_UID {
+    return [NSString stringWithFormat:@"%lu",(uintptr_t)self];
+}
+
+@end

src/UIView+Frank.h

@@ -0,0 +1,14 @@
+//
+//  UIView+Frank.h
+//  Frank
+//
+//  Created by Toshiyuki Suzumura on 2013/07/04.
+//
+
+#import <UIKit/UIKit.h>
+
+@interface UIView (Frank)
+
+- (NSString *) FEX_UID;
+
+@end

src/UIView+Frank.m

@@ -6,7 +6,7 @@
 //  Copyright (c) 2012 ThoughtWorks. All rights reserved.
 //
 
-
+#import "UIView+Frank.h"
 #import "LoadableCategory.h"
 
 MAKE_CATEGORIES_LOADABLE(UIView_Frank)
@@ -51,4 +51,8 @@ - (BOOL)FEX_isFullyWithinWindow {
     return CGRectContainsRect(self.window.bounds, myFrameInWindowCoords);
 }
 
+- (NSString *) FEX_UID {
+    return [NSString stringWithFormat:@"%i",(int)self];
+}
+
 @end