src/osx/core/glgrab.cpp

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  31  */
  32
  33 #include "wx/wxprec.h"
  34
  35 #if wxOSX_USE_COCOA_OR_CARBON
  36
  37 #import <CoreFoundation/CoreFoundation.h>
  38 #import <ApplicationServices/ApplicationServices.h>
  39 #import <OpenGL/OpenGL.h>
  40 #import <OpenGL/gl.h>
  41
  42 #include "wx/osx/private/glgrab.h"
  43
  44 extern CGColorSpaceRef wxMacGetGenericRGBColorSpace();
  45
  46 /*
  47  * perform an in-place swap from Quadrant 1 to Quadrant III format
  48  * (upside-down PostScript/GL to right side up QD/CG raster format)
  49  * We do this in-place, which requires more copying, but will touch
  50  * only half the pages.  (Display grabs are BIG!)
  51  *
  52  * Pixel reformatting may optionally be done here if needed.
  53  */
  54 static void swizzleBitmap(void * data, int rowBytes, int height)
  55 {
  56     int top, bottom;
  57     void * buffer;
  58     void * topP;
  59     void * bottomP;
  60     void * base;
  61
  62
  63     top = 0;
  64     bottom = height - 1;
  65     base = data;
  66     buffer = malloc(rowBytes);
  67
  68
  69     while ( top < bottom )
  70     {
  71         topP = (void *)((top * rowBytes) + (intptr_t)base);
  72         bottomP = (void *)((bottom * rowBytes) + (intptr_t)base);
  73
  74
  75         /*
  76          * Save and swap scanlines.
  77          *
  78          * This code does a simple in-place exchange with a temp buffer.
  79          * If you need to reformat the pixels, replace the first two bcopy()
  80          * calls with your own custom pixel reformatter.
  81          */
  82         bcopy( topP, buffer, rowBytes );
  83         bcopy( bottomP, topP, rowBytes );
  84         bcopy( buffer, bottomP, rowBytes );
  85
  86         ++top;
  87         --bottom;
  88     }
  89     free( buffer );
  90 }
  91
  92
  93 /*
  94  * Given a display ID and a rectangle on that display, generate a CGImageRef
  95  * containing the display contents.
  96  *
  97  * srcRect is display-origin relative.
  98  *
  99  * This function uses a full screen OpenGL read-only context.
 100  * By using OpenGL, we can read the screen using a DMA transfer
 101  * when it's in millions of colors mode, and we can correctly read
 102  * a microtiled full screen OpenGL context, such as a game or full
 103  * screen video display.
 104  *
 105  * Returns a CGImageRef. When you are done with the CGImageRef, release it
 106  * using CFRelease().
 107  * Returns NULL on an error.
 108  */
 109
 110 CGImageRef grabViaOpenGL(CGDirectDisplayID display, CGRect srcRect)
 111 {
 112     CGContextRef bitmap;
 113     CGImageRef image;
 114     void * data;
 115     long bytewidth;
 116     GLint width, height;
 117     long bytes;
 118
 119     CGLContextObj    glContextObj;
 120     CGLPixelFormatObj pixelFormatObj ;
 121     GLint numPixelFormats ;
 122     CGLPixelFormatAttribute attribs[] =
 123     {
 124         kCGLPFAFullScreen,
 125         kCGLPFADisplayMask,
 126         (CGLPixelFormatAttribute) 0,    /* Display mask bit goes here */
 127         (CGLPixelFormatAttribute) 0
 128     } ;
 129
 130
 131     if ( display == kCGNullDirectDisplay )
 132         display = CGMainDisplayID();
 133     attribs[2] = (CGLPixelFormatAttribute) CGDisplayIDToOpenGLDisplayMask(display);
 134
 135
 136     /* Build a full-screen GL context */
 137     CGLChoosePixelFormat( attribs, &pixelFormatObj, &numPixelFormats );
 138     if ( pixelFormatObj == NULL )    // No full screen context support
 139         return NULL;
 140     CGLCreateContext( pixelFormatObj, NULL, &glContextObj ) ;
 141     CGLDestroyPixelFormat( pixelFormatObj ) ;
 142     if ( glContextObj == NULL )
 143         return NULL;
 144
 145
 146     CGLSetCurrentContext( glContextObj ) ;
 147     CGLSetFullScreen( glContextObj ) ;
 148
 149
 150     glReadBuffer(GL_FRONT);
 151
 152
 153     width = (GLint)srcRect.size.width;
 154     height = (GLint)srcRect.size.height;
 155
 156
 157     bytewidth = width * 4; // Assume 4 bytes/pixel for now
 158     bytewidth = (bytewidth + 3) & ~3; // Align to 4 bytes
 159     bytes = bytewidth * height; // width * height
 160
 161     /* Build bitmap context */
 162     data = malloc(height * bytewidth);
 163     if ( data == NULL )
 164     {
 165         CGLSetCurrentContext( NULL );
 166         CGLClearDrawable( glContextObj ); // disassociate from full screen
 167         CGLDestroyContext( glContextObj ); // and destroy the context
 168         return NULL;
 169     }
 170     bitmap = CGBitmapContextCreate(data, width, height, 8, bytewidth,
 171                                    wxMacGetGenericRGBColorSpace(), kCGImageAlphaNoneSkipFirst /* XRGB */);
 172
 173
 174     /* Read framebuffer into our bitmap */
 175     glFinish(); /* Finish all OpenGL commands */
 176     glPixelStorei(GL_PACK_ALIGNMENT, 4); /* Force 4-byte alignment */
 177     glPixelStorei(GL_PACK_ROW_LENGTH, 0);
 178     glPixelStorei(GL_PACK_SKIP_ROWS, 0);
 179     glPixelStorei(GL_PACK_SKIP_PIXELS, 0);
 180
 181     /*
 182      * Fetch the data in XRGB format, matching the bitmap context.
 183      */
 184     glReadPixels((GLint)srcRect.origin.x, (GLint)srcRect.origin.y, width, height,
 185                  GL_BGRA,
 186 #ifdef __BIG_ENDIAN__
 187                  GL_UNSIGNED_INT_8_8_8_8_REV, // for PPC
 188 #else
 189                  GL_UNSIGNED_INT_8_8_8_8, // for Intel! http://lists.apple.com/archives/quartz-dev/2006/May/msg00100.html
 190 #endif
 191                  data);
 192     /*
 193      * glReadPixels generates a quadrant I raster, with origin in the lower left
 194      * This isn't a problem for signal processing routines such as compressors,
 195      * as they can simply use a negative 'advance' to move between scanlines.
 196      * CGImageRef and CGBitmapContext assume a quadrant III raster, though, so we need to
 197      * invert it. Pixel reformatting can also be done here.
 198      */
 199     swizzleBitmap(data, bytewidth, height);
 200
 201
 202     /* Make an image out of our bitmap; does a cheap vm_copy of the bitmap */
 203     image = CGBitmapContextCreateImage(bitmap);
 204
 205     /* Get rid of bitmap */
 206     CFRelease(bitmap);
 207     free(data);
 208
 209
 210     /* Get rid of GL context */
 211     CGLSetCurrentContext( NULL );
 212     CGLClearDrawable( glContextObj ); // disassociate from full screen
 213     CGLDestroyContext( glContextObj ); // and destroy the context
 214
 215     /* Returned image has a reference count of 1 */
 216     return image;
 217 }
 218
 219 #endif