src/osx/core/glgrab.cpp

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