src/fl_read_image_win32.cxx

   1 //
   2 // "$Id: fl_read_image_win32.cxx 8595 2011-04-17 08:48:40Z manolo $"
   3 //
   4 // WIN32 image reading routines for the Fast Light Tool Kit (FLTK).
   5 //
   6 // Copyright 1998-2010 by Bill Spitzak and others.
   7 //
   8 // This library is free software; you can redistribute it and/or
   9 // modify it under the terms of the GNU Library General Public
  10 // License as published by the Free Software Foundation; either
  11 // version 2 of the License, or (at your option) any later version.
  12 //
  13 // This library is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 // Library General Public License for more details.
  17 //
  18 // You should have received a copy of the GNU Library General Public
  19 // License along with this library; if not, write to the Free Software
  20 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  21 // USA.
  22 //
  23 // Please report all bugs and problems on the following page:
  24 //
  25 //     http://www.fltk.org/str.php
  26 //
  27
  28 //
  29 // 'fl_read_image()' - Read an image from the current window.
  30 //
  31
  32 uchar *                         // O - Pixel buffer or NULL if failed
  33 fl_read_image(uchar *p,         // I - Pixel buffer or NULL to allocate
  34               int   X,          // I - Left position
  35               int   Y,          // I - Top position
  36               int   w,          // I - Width of area to read
  37               int   h,          // I - Height of area to read
  38               int   alpha) {    // I - Alpha value for image (0 for none)
  39
  40   int   d;                      // Depth of image
  41
  42   // Allocate the image data array as needed...
  43   d = alpha ? 4 : 3;
  44
  45   if (!p) p = new uchar[w * h * d];
  46
  47   // Initialize the default colors/alpha in the whole image...
  48   memset(p, alpha, w * h * d);
  49
  50   // Grab all of the pixels in the image...
  51
  52   // Assure that we are not trying to read non-existing data. If it is so, the
  53   // function should still work, but the out-of-bounds part of the image is
  54   // untouched (initialized with the alpha value or 0 (black), resp.).
  55
  56   int ww = w; // We need the original width for output data line size
  57
  58   int shift_x = 0; // X target shift if X modified
  59   int shift_y = 0; // Y target shift if X modified
  60
  61   if (X < 0) {
  62     shift_x = -X;
  63     w += X;
  64     X = 0;
  65   }
  66   if (Y < 0) {
  67     shift_y = -Y;
  68     h += Y;
  69     Y = 0;
  70   }
  71
  72   if (h < 1 || w < 1) return p;         // nothing to copy
  73
  74   int line_size = ((3*w+3)/4) * 4;      // each line is aligned on a DWORD (4 bytes)
  75   uchar *dib = new uchar[line_size*h];  // create temporary buffer to read DIB
  76
  77   // fill in bitmap info for GetDIBits
  78
  79   BITMAPINFO   bi;
  80   bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
  81   bi.bmiHeader.biWidth = w;
  82   bi.bmiHeader.biHeight = -h;           // negative => top-down DIB
  83   bi.bmiHeader.biPlanes = 1;
  84   bi.bmiHeader.biBitCount = 24;         // 24 bits RGB
  85   bi.bmiHeader.biCompression = BI_RGB;
  86   bi.bmiHeader.biSizeImage = 0;
  87   bi.bmiHeader.biXPelsPerMeter = 0;
  88   bi.bmiHeader.biYPelsPerMeter = 0;
  89   bi.bmiHeader.biClrUsed = 0;
  90   bi.bmiHeader.biClrImportant = 0;
  91
  92   // copy bitmap from original DC (Window, Fl_Offscreen, ...)
  93
  94   HDC hdc = CreateCompatibleDC(fl_gc);
  95   HBITMAP hbm = CreateCompatibleBitmap(fl_gc,w,h);
  96
  97   int save_dc = SaveDC(hdc);                    // save context for cleanup
  98   SelectObject(hdc,hbm);                        // select bitmap
  99   BitBlt(hdc,0,0,w,h,fl_gc,X,Y,SRCCOPY);        // copy image section to DDB
 100
 101   // copy RGB image data to the allocated DIB
 102
 103   GetDIBits(hdc, hbm, 0, h, dib, (BITMAPINFO *)&bi, DIB_RGB_COLORS);
 104
 105   // finally copy the image data to the user buffer
 106
 107   for (int j = 0; j<h; j++) {
 108     const uchar *src = dib + j * line_size;                     // source line
 109     uchar *tg = p + (j + shift_y) * d * ww + shift_x * d;       // target line
 110     for (int i = 0; i<w; i++) {
 111       uchar b = *src++;
 112       uchar g = *src++;
 113       *tg++ = *src++;   // R
 114       *tg++ = g;        // G
 115       *tg++ = b;        // B
 116       if (alpha)
 117         *tg++ = alpha;  // alpha
 118     }
 119   }
 120
 121   // free used GDI and other structures
 122
 123   RestoreDC(hdc,save_dc);       // reset DC
 124   DeleteDC(hdc);
 125   DeleteObject(hbm);
 126   delete[] dib;         // delete DIB temporary buffer
 127
 128   return p;
 129 }
 130
 131 //
 132 // End of "$Id: fl_read_image_win32.cxx 8595 2011-04-17 08:48:40Z manolo $".
 133 //