Screen Capture problem

[berus4]

Hello. I have problem witch this code:
- (NSImage*) captureScreen
{
int bitsPP, w, h;
int bytesPerRow, bytesPerPixel, numRowBytes;
unsigned char* srcPixels;
unsigned char* dstPixels;
unsigned long index, pRow, srcPix, dstPix, rowLen;
NSImage* resImg;
NSBitmapImageRep* bmapRep;

// screen width & height
w = CGDisplayPixelsWide(kCGDirectMainDisplay );
h = CGDisplayPixelsHigh(kCGDirectMainDisplay );
srcPixels = (unsigned char*) CGDisplayBaseAddress(kCGDirectMainDisplay);
dstPixels = (unsigned char*) malloc( w * h * 4);
bitsPP = CGDisplayBitsPerPixel(kCGDirectMainDisplay);
bytesPerRow = CGDisplayBytesPerRow(kCGDirectMainDisplay);
bytesPerPixel = bitsPP >> 3;

if ( dstPixels != 0 )
{
int y;

numRowBytes = (w * 4);
for (y=0; y < h; y++)
{
rowLen = (unsigned long)(y * bytesPerRow);

for (index=0; index < w; index++)
{
pRow = (index * bytesPerPixel) + rowLen;
srcPix = *((unsigned long*)(srcPixels + pRow));
dstPix = (srcPix >> 24) | ((srcPix & 0x00FFFFFF) << 8);
*((unsigned long*)(dstPixels + pRow)) = dstPix;
}
}
}

bmapRep = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:&dstPixels
pixelsWide:w
pixelsHigh:h bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSDeviceRGBColorSpace
bytesPerRow:numRowBytes
bitsPerPixel:32];

resImg = [[NSImage alloc] initWithSize:[bmapRep size]];
if ( resImg != nil )
{
[resImg addRepresentation:bmapRep];
} else {
NSLog(@"Image is nil");
}
[bmapRep release];
return resImg;
}

It should make screenshot but when i want to make it application crashes and exit. Do anybody now what is the problem?

[Fenris]

Please post the crash log, otherwise it's next to impossible to figure it out. :)

[berus4]

This is it:
[Session started at 2007-04-15 11:45:27 +0200.]
2007-04-15 11:45:32.607 Fotka[294] *** Message from <QCVideoInput = 0x003BA180 "VideoInput_1">:
Sequence grabber initialization failed (error -9405)
ZeroLink: unknown symbol '_captureScreen'

Fotka has exited due to signal 6 (SIGABRT).

[OneSadCookie]

Don't try and call an ObjC method as if it were a C function.

Also, don't ignore the compiler warnings!

[berus4]

OK. It works. Thanks. But do anybody now how to speed up this code?

[berus4]

To speed up this code i split it to:

@implementation AppController

unsigned char* srcPixels;
unsigned char* dstPixels;
unsigned int indeks, pRow, srcPix, dstPix, rowLen, _u;
int bitsPP, w, h;
int bytesPerRow, bytesPerPixel, numRowBytes;
NSImage* resImg;
NSBitmapImageRep* bmapRep;

- (void) awakeFromNib
{
//Główne informacje zbieranie itp...
w = CGDisplayPixelsWide(kCGDirectMainDisplay );
h = CGDisplayPixelsHigh(kCGDirectMainDisplay );
srcPixels = (unsigned char*) CGDisplayBaseAddress(kCGDirectMainDisplay);
dstPixels = (unsigned char*) malloc( w * h * 4);
bitsPP = CGDisplayBitsPerPixel(kCGDirectMainDisplay);
bytesPerRow = CGDisplayBytesPerRow(kCGDirectMainDisplay);
bytesPerPixel = bitsPP >> 3;
numRowBytes = (w * 4);


}

- (NSImage*) captureScreen
{


for (y=0; y < h; y++)
{
rowLen = y * bytesPerRow;

for (indeks=0; indeks < w; indeks++)
{
pRow = (indeks * bytesPerPixel) + rowLen;
srcPix = *((int*)(srcPixels + pRow));
dstPix = (srcPix >> 24) | ((srcPix & 0x00FFFFFF) << 8);
*((int*)(dstPixels + pRow)) = dstPix;
}
}


bmapRep = [[NSBitmapImageRep alloc]
initWithBitmapDataPlanes:&dstPixels
pixelsWide:w
pixelsHigh:h
bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSDeviceRGBColorSpace
bytesPerRow:numRowBytes
bitsPerPixel:32];

resImg = [[NSImage alloc] initWithSize:[bmapRep size]];
[resImg addRepresentation:bmapRep];
return resImg;
}

But it is still to slow.

[OneSadCookie]

What is "too slow" ?

Reading from video memory is always going to be slow.

The usual way to take a screenshot is to use glReadPixels from a full-screen CGL context without capturing the display first. At least that way you should get a DMA to system memory, and you won't be assuming anything about the framebuffer format as you currently do.

[berus4]

OK. I found a magnification glass example but it is in Carbon:

/*
File: Magnify.cp

Contains: Sample application which implements a magnifying lens tool.

Version: Mac OS X

Disclaimer: IMPORTANT: This Apple software is supplied to you by Apple Computer, Inc.
("Apple") in consideration of your agreement to the following terms, and your
use, installation, modification or redistribution of this Apple software
constitutes acceptance of these terms. If you do not agree with these terms,
please do not use, install, modify or redistribute this Apple software.

In consideration of your agreement to abide by the following terms, and subject
to these terms, Apple grants you a personal, non-exclusive license, under Apple’s
copyrights in this original Apple software (the "Apple Software"), to use,
reproduce, modify and redistribute the Apple Software, with or without
modifications, in source and/or binary forms; provided that if you redistribute
the Apple Software in its entirety and without modifications, you must retain
this notice and the following text and disclaimers in all such redistributions of
the Apple Software. Neither the name, trademarks, service marks or logos of
Apple Computer, Inc. may be used to endorse or promote products derived from the
Apple Software without specific prior written permission from Apple. Except as
expressly stated in this notice, no other rights or licenses, express or implied,
are granted by Apple herein, including but not limited to any patent rights that
may be infringed by your derivative works or by other works in which the Apple
Software may be incorporated.

The Apple Software is provided by Apple on an "AS IS" basis. APPLE MAKES NO
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED
WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN
COMBINATION WITH YOUR PRODUCTS.

IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, MODIFICATION AND/OR DISTRIBUTION
OF THE APPLE SOFTWARE, HOWEVER CAUSED AND WHETHER UNDER THEORY OF CONTRACT, TORT
(INCLUDING NEGLIGENCE), STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Copyright © 1997-2001 Apple Computer, Inc., All Rights Reserved
*/

#include <Carbon/Carbon.h>

enum
{
kCmdMagnificationChanged = 'MChg',
kCmdShowMouseLocation = 'MLoc',
kCmdFloat = 'Floa'
};

struct PrefInfo
{
UInt8 origMagFactor;
Boolean origShowInfo;
Boolean origFloats;
WindowRef window;
};
typedef struct PrefInfo PrefInfo;

static OSStatus WindowHandler( EventHandlerCallRef inHandler, EventRef inEvent, void* userData );
static OSStatus AppCommandHandler( EventHandlerCallRef inHandler, EventRef inEvent, void* userData );
static OSStatus PrefHandler( EventHandlerCallRef inHandler, EventRef inEvent, void* userData );

static void DoPreferences();
static void AdjustWindowFloating();

static GrafPtr sGlobalPort = NULL;
static UInt8 sMagFactor = 8;
static Boolean sShowInfo = true;
static Boolean sFloats = false;
static Boolean sForceUpdate = false;
static WindowRef sMagnifyWindow;

static const ControlID kMagSlider = { 'PREF', 1 };
static const ControlID kShowInfoCheck = { 'PREF', 2 };
static const ControlID kFloatCheck = { 'PREF', 3 };

#define kPreferencesKey CFSTR( "com.apple.carbon.examples.magnify" )

//----------------------------------------------------------------------------
// • MagnifyEventLoopTimer
//
// Our magnification timer. Ideally we should be event based, but we can't
// detect every event that might cause a screen update (window move, etc.)
// so we resort to this.
//----------------------------------------------------------------------------

pascal void
MagnifyEventLoopTimer(EventLoopTimerRef /*inTimer*/, void *inUserData)
{
WindowRef window = (WindowRef)inUserData;
Point mouse;
GrafPtr windowPort;
GrafPtr savePort;
Rect sourceRect;
Rect destRect;
Rect portBounds;
SInt16 distance;
static Point sLastMouse = { -1, -1};

GetPort( &savePort );
windowPort = GetWindowPort(window);

GetPortBounds( windowPort, &portBounds );

GetGlobalMouse( &mouse );

if ( !EqualPt( mouse, sLastMouse ) || sForceUpdate )
{
Rect monitorBounds;
SInt32 temp;

sLastMouse = mouse;
SetPort(windowPort);

distance = SInt16((portBounds.right - portBounds.left) / (sMagFactor * 2));

// Pin the mouse position to the main monitor
monitorBounds = (**GetMainDevice()).gdRect;

InsetRect( &monitorBounds, distance, distance );

temp = PinRect( &monitorBounds, mouse );
mouse.v = HiWord(temp);
mouse.h = LoWord(temp);

sourceRect.left = mouse.h - distance;
sourceRect.right = mouse.h + distance;
sourceRect.top = mouse.v - distance;
sourceRect.bottom = mouse.v + distance;

destRect = portBounds;

ForeColor(blackColor);
BackColor(whiteColor);
PenMode( srcCopy );

CopyBits( *(BitMap **)GetPortPixMap(sGlobalPort), *(BitMap **)GetPortPixMap(windowPort), &sourceRect, &destRect, srcCopy, NULL );

if ( sShowInfo )
{
CFStringRef string;

string = CFStringCreateWithFormat( NULL, NULL, CFSTR( "(%d,%d), %dx" ), sLastMouse.h, sLastMouse.v, sMagFactor );

if ( string )
{
Rect box;
Point size;
SInt16 baseLine;
const RGBColor kWhite = { 0xFFFF, 0xFFFF, 0xFFFF };
const RGBColor kBlack = { 0, 0, 0 };

TextFont( 0 );
TextSize( 12 );

GetThemeTextDimensions( string, kThemeCurrentPortFont, kThemeStateActive,
false, &size, &baseLine );

box.left = portBounds.left;
box.bottom = portBounds.bottom;
box.right = box.left + size.h;
box.top = box.bottom - size.v;

RGBForeColor( &kBlack );
PaintRect( &box );

RGBForeColor( &kWhite );
DrawThemeTextBox( string, kThemeCurrentPortFont, kThemeStateActive,
false, &box, teCenter, NULL );

CFRelease( string );
}
}


ForeColor( blackColor );
BackColor( whiteColor );
PenMode( patXor );

MoveTo( ( portBounds.right / 2 ) - 4, portBounds.bottom / 2 );
Line( 8, 0 );
MoveTo( portBounds.right / 2, ( portBounds.bottom / 2 ) - 4 );
Line( 0, 8 );

SetPort( savePort );
}

sForceUpdate = false;
}

//----------------------------------------------------------------------------
// • CreateMagnifyWindow
//
// Create our magnification window.
//----------------------------------------------------------------------------

static OSStatus
CreateMagnifyWindow( IBNibRef nibRef )
{
WindowRef window;
EventLoopTimerUPP eventLoopTimer;
EventHandlerRef eventHandlerRef;
EventHandlerUPP handlerProc;
EventTypeSpec events[] = { { kEventClassWindow, kEventWindowBoundsChanging } };
OSStatus err;

err = CreateWindowFromNib( nibRef, CFSTR( "MainWindow" ), &window );
require_noerr( err, CantCreateWindow );

// Now install our own handler so we can intercept window size changes
// For this handler, plus our timer below, we create a UPP, but we never
// dispose of it. This is because our window stays around until we quit.
// If we had a window that came and went, we would need to clean up
// properly and Dispose the EventHandlerUPP and the EventLoopTimerUPP for
// the window.

handlerProc = NewEventHandlerUPP( WindowHandler );
verify_noerr( InstallWindowEventHandler( window, handlerProc, GetEventTypeCount( events ),
events, window, &eventHandlerRef ) );

// Install our timer, which we use to update the window.

eventLoopTimer = NewEventLoopTimerUPP(MagnifyEventLoopTimer);

verify_noerr( InstallEventLoopTimer( GetCurrentEventLoop(), kEventDurationSecond,
kEventDurationSecond / 20, eventLoopTimer, (void *)window, NULL ) );

// Make this window such that it does not hide when we are suspended.
// Normally, floating windows have the hide-on-suspend attribute set
// so that they hide when switching out and show when resumed later.

ChangeWindowAttributes( window, 0, kWindowHideOnSuspendAttribute );

sMagnifyWindow = window;

// Adjust our float-ness as per our current settings

AdjustWindowFloating();

// And it's always nice to see the windows we create.

ShowWindow(window);

CantCreateWindow:
return err;
}

//----------------------------------------------------------------------------
// • WindowHandler
//
// Constrain our resizing to a perfect square.
//----------------------------------------------------------------------------

static OSStatus
WindowHandler( EventHandlerCallRef inHandler, EventRef inEvent, void* userData )
{
Rect bounds;
SInt16 height, width;
UInt32 attributes;
OSStatus result = eventNotHandledErr;

GetEventParameter( inEvent, kEventParamAttributes, typeUInt32, NULL, sizeof( UInt32 ), NULL, &attributes );

// We only constrain on size changes. There is no point constraining if
// the position (origin) is changing.

if ( (attributes & kWindowBoundsChangeSizeChanged) != 0 )
{
// Extract the current bounds. This is the paramter you get to modify to
// alter the window position or size during a window resizing.
GetEventParameter( inEvent, kEventParamCurrentBounds, typeQDRectangle, NULL, sizeof( bounds ), NULL, &bounds );

// Make the bounds square
height = bounds.bottom - bounds.top;
width = bounds.right - bounds.left;

if ( width > height )
{
bounds.bottom = bounds.top + width;
}
else
{
bounds.right = bounds.left + height;
}

// Set the current bounds parameter to our adjusted bounds. Return
// noErr to indicate we handled this event.
SetEventParameter( inEvent, kEventParamCurrentBounds, typeQDRectangle, sizeof( bounds ), &bounds );
result = noErr;
}
return result;
}

//----------------------------------------------------------------------------
// • main
//
// Where it all begins...
//----------------------------------------------------------------------------

int main( int argc, char* argv[] )
{
OSStatus err = noErr;
IBNibRef nibRef;
EventTypeSpec cmdEvent = { kEventClassCommand, kEventCommandProcess };
Boolean test;

// Make sure the arrow cursor is displayed

InitCursor();

// Open our nib and set up the menu bar from it

err = CreateNibReference( CFSTR( "Magnify" ), &nibRef );
require_noerr( err, CantOpenNib );

err = SetMenuBarFromNib( nibRef, CFSTR( "MainMenu" ) );
require_noerr( err, CantSetMenuBar );

// We have a preference dialog, so we need to activate
// the Preferences menu item in our Application menu.
// The way to do that is by command ID. Normally, this
// menu item is disabled.

EnableMenuCommand( NULL, kHICommandPreferences );

// Create a global port so we can copy bits from the screen

sGlobalPort = CreateNewPort();
require_noerr( QDError(), NewPortFailed );

// Let's see the menu bar, please.

DrawMenuBar();

// Load any prefs. We use CFPreferences to store our preferences.
// When doing this, you need to create a key for your application.
// Normally this is the bundle ID of your app.

sShowInfo = CFPreferencesGetAppBooleanValue( CFSTR( "ShowInfo" ), kPreferencesKey, &test );
if ( !test ) sShowInfo = true;

sMagFactor = CFPreferencesGetAppIntegerValue( CFSTR( "MagFactor" ), kPreferencesKey, &test );
if ( !test ) sMagFactor = 8;

sFloats = CFPreferencesGetAppBooleanValue( CFSTR( "Float" ), kPreferencesKey, &test );
if ( !test ) sFloats = false;

// Now create our window and dispose the nib ref - we're done with it.

CreateMagnifyWindow( nibRef );
DisposeNibReference( nibRef );

// Because we want to respond to the preferences menu item, we need to
// install a command handler to handle the menu selection. Here we are
// creating the UPP on the fly and not disposing it, since it will get
// destroyed when the app terminates.

InstallApplicationEventHandler( NewEventHandlerUPP( AppCommandHandler ), 1, &cmdEvent, 0, NULL );

// Run Lola, Run!

RunApplicationEventLoop();

// Clean up and exit.

DisposePort( sGlobalPort );

return noErr;

NewPortFailed:
CantSetMenuBar:
DisposeNibReference( nibRef );

CantOpenNib:
return err;
}

//----------------------------------------------------------------------------
// • AppCommandHandler
//
// Look for the preferences menu item and call DoPreferences when we
// receive it.
//----------------------------------------------------------------------------

static OSStatus
AppCommandHandler( EventHandlerCallRef inHandler, EventRef inEvent, void* inUserData )
{
#pragma unused( inHandler, inUserData )

HICommand cmd;
OSStatus result = eventNotHandledErr;

GetEventParameter( inEvent, kEventParamDirectObject, typeHICommand, NULL, sizeof( cmd ), NULL, &cmd );
if ( cmd.commandID == kHICommandPreferences )
{
DoPreferences();
result = noErr;
}

return result;
}

//----------------------------------------------------------------------------
// • DoPreferences
//
// Open our preferences dialog and run it modally.
//----------------------------------------------------------------------------

static void
DoPreferences()
{
IBNibRef nibRef;
EventTypeSpec cmdEvent = { kEventClassCommand, kEventCommandProcess };
WindowRef window;
OSStatus err;
ControlRef control;
PrefInfo info;
EventHandlerUPP handler;

// Open our nib, create the window, and close the nib.
err = CreateNibReference( CFSTR( "Magnify" ), &nibRef );
require_noerr( err, CantOpenNib );

err = CreateWindowFromNib( nibRef, CFSTR( "Preferences" ), &window );
require_noerr( err, CantCreateWindow );

DisposeNibReference( nibRef );

// For each control of interest, set its value as appropriate
// for the settings we currently have.

GetControlByID( window, &kMagSlider, &control );
SetControlValue( control, (sMagFactor >> 2) + 1 );

GetControlByID( window, &kShowInfoCheck, &control );
SetControlValue( control, sShowInfo );

GetControlByID( window, &kFloatCheck, &control );
SetControlValue( control, sFloats );

// Build up a structure to pass to the window handler we are about
// to install. We store the window itself, as well as the original
// states of our settings. We use this to revert if the user clicks
// the cancel button.

info.window = window;
info.origMagFactor = sMagFactor;
info.origShowInfo = sShowInfo;
info.origFloats = sFloats;

// Now create our UPP and install the handler.

handler = NewEventHandlerUPP( PrefHandler );
InstallWindowEventHandler( window, handler, 1, &cmdEvent, &info, NULL );

// Position and show the window

RepositionWindow( window, NULL, kWindowAlertPositionOnMainScreen );
ShowWindow( window );

// Now we run modally. We will remain here until the PrefHandler
// calls QuitAppModalLoopForWindow if the user clicks OK or
// Cancel.

RunAppModalLoopForWindow( window );

// OK, we're done. Dispose of our window and our UPP.
// We do the UPP last because DisposeWindow can send out
// CarbonEvents, and we haven't explicitly removed our
// handler. If we disposed the UPP, the Toolbox might try
// to call it. That would be bad.

DisposeWindow( window );
DisposeEventHandlerUPP( handler );

return;

CantCreateWindow:
DisposeNibReference( nibRef );

CantOpenNib:
return;
}

//----------------------------------------------------------------------------
// • PrefHandler
//
// Our command handler for the Preferences dialog.
//----------------------------------------------------------------------------

static OSStatus
PrefHandler( EventHandlerCallRef inHandler, EventRef inEvent, void* inUserData )
{
#pragma unused( inHandler )

HICommand cmd;
OSStatus result = eventNotHandledErr;
PrefInfo* info = (PrefInfo*)inUserData;
ControlRef control;
CFNumberRef number;
WindowRef window = info->window;

// The direct object for a 'process commmand' event is the HICommand.
// Extract it here and switch off the command ID.

GetEventParameter( inEvent, kEventParamDirectObject, typeHICommand, NULL, sizeof( cmd ), NULL, &cmd );

switch ( cmd.commandID )
{
case kHICommandOK:
number = CFNumberCreate( NULL, kCFNumberSInt8Type, &sMagFactor );
CFPreferencesSetAppValue( CFSTR( "MagFactor" ), number, kPreferencesKey );
CFPreferencesSetAppValue( CFSTR( "ShowInfo" ), sShowInfo ? kCFBooleanTrue : kCFBooleanFalse, kPreferencesKey );
CFPreferencesSetAppValue( CFSTR( "Float" ), sFloats ? kCFBooleanTrue : kCFBooleanFalse, kPreferencesKey );
CFPreferencesAppSynchronize( kPreferencesKey );
CFRelease( number );

QuitAppModalLoopForWindow( window );
result = noErr;
break;

case kHICommandCancel:
sMagFactor = info->origMagFactor;
sShowInfo = info->origShowInfo;
sFloats = info->origFloats;
AdjustWindowFloating();
sForceUpdate = true;
QuitAppModalLoopForWindow( window );
result = noErr;
break;

case kCmdMagnificationChanged:
GetControlByID( window, &kMagSlider, &control );
sMagFactor = 2 << (GetControlValue( control ) - 1);
sForceUpdate = true;
result = noErr;
break;

case kCmdShowMouseLocation:
GetControlByID( window, &kShowInfoCheck, &control );
sShowInfo = GetControlValue( control );
sForceUpdate = true;
result = noErr;
break;

case kCmdFloat:
GetControlByID( window, &kFloatCheck, &control );
sFloats = GetControlValue( control );
AdjustWindowFloating();
result = noErr;
break;
}
return result;
}

//----------------------------------------------------------------------------
// • AdjustWindowFloating
//
// Adjust our window's floating state based on the current setting. We can
// either float in our application's layer, or above all applications. We
// accomplish this magic by moving the window between the appropriate window
// groups.
//----------------------------------------------------------------------------

static void
AdjustWindowFloating()
{
check( sMagnifyWindow != NULL );

if ( sFloats )
SetWindowGroup( sMagnifyWindow, GetWindowGroupOfClass( kUtilityWindowClass ) );
else
SetWindowGroup( sMagnifyWindow, GetWindowGroupOfClass( kFloatingWindowClass ) );
}
I dont know Carbon and i little now about Cocoa. Could somebody get the code what gets screen image?

[OneSadCookie]

You don't want to do it that way. QuickDraw is deprecated, and I can't imagine that CopyBits from VRAM is any much better than your original method.

[berus4]

OK. Im programing in xCode 1 week and i have mac about 3 weeks. I have learn xCode and obj-C from developer.apple.com and i dont get many things about it.

[arekkusu]

There is an old piece of OpenGL sample code which is closer to what you want.
It is not supported by Apple any more though, so you have to grab it off the ftp archive:

ftp://ftp.apple.com/developer/Sample_Code/Archive/Graphics/glGrab.sit

[berus4]

OK. It works. Big Thanks

[leRiCl]

Do you find apple.com lacks alot of example code? If it weren't for google.com, I'd never have thought you needed a "Dictionary" just to create a directory bundle or even just a toolbar. But then maybe I am just too newbie to be learning more than just BASIC and Java. (uhh, catch-22. While I not learn lower level languages I will always remain a newbie and unable to enter, hah.)