Author: AlbrechtS
Date: 2010-12-16 12:23:57 -0800 (Thu, 16 Dec 2010)
New Revision: 8048
Log:
This new fl_read_image() function for Windows is *much* faster than
reading individual pixels as before (STR #2387), but there is still
room for improvement...
Modified:
branches/branch-1.3/CHANGES
branches/branch-1.3/src/fl_read_image_win32.cxx
Modified: branches/branch-1.3/CHANGES
===================================================================
--- branches/branch-1.3/CHANGES 2010-12-16 10:28:27 UTC (rev 8047)
+++ branches/branch-1.3/CHANGES 2010-12-16 20:23:57 UTC (rev 8048)
@@ -1,5 +1,6 @@
CHANGES IN FLTK 1.3.0
+ - Much faster fl_read_image() for Windows (STR #2387).
- Added general Options dialog (STR #2471)
- Fixed Compiling with mingw-w64 (STR #2308).
- Fixed crashes when detecting illegal utf 8 sequences
Modified: branches/branch-1.3/src/fl_read_image_win32.cxx
===================================================================
--- branches/branch-1.3/src/fl_read_image_win32.cxx 2010-12-16 10:28:27 UTC
(rev 8047)
+++ branches/branch-1.3/src/fl_read_image_win32.cxx 2010-12-16 20:23:57 UTC
(rev 8048)
@@ -36,11 +36,9 @@
int w, // I - Width of area to read
int h, // I - Height of area to read
int alpha) { // I - Alpha value for image (0 for none)
- int x, y; // Looping vars
+
int d; // Depth of image
- uchar *ptr; // Pointer in image data
-
// Allocate the image data array as needed...
d = alpha ? 4 : 3;
@@ -49,24 +47,87 @@
// Initialize the default colors/alpha in the whole image...
memset(p, alpha, w * h * d);
- // Grab all of the pixels in the image, one at a time...
- // MRS: there has to be a better way than this!
- for (y = 0, ptr = p; y < h; y ++) {
- for (x = 0; x < w; x ++, ptr += d) {
- COLORREF c = GetPixel(fl_gc, X + x, Y + y);
+ // Grab all of the pixels in the image...
- ptr[0] = (uchar)c;
- c >>= 8;
- ptr[1] = (uchar)c;
- c >>= 8;
- ptr[2] = (uchar)c;
+ // Assure that we are not trying to read non-existing data. If it is so, the
+ // function should still work, but the out-of-bounds part of the image is
+ // untouched (initialized with the alpha value or 0 (black), resp.).
+
+ int ww = w; // We need the original width for output data line size
+
+ int shift_x = 0; // X target shift if X modified
+ int shift_y = 0; // Y target shift if X modified
+
+ if (X < 0) {
+ shift_x = -X;
+ w += X;
+ X = 0;
+ }
+ if (Y < 0) {
+ shift_y = -Y;
+ h += Y;
+ Y = 0;
+ }
+
+ if (h < 1 || w < 1) return p; // nothing to copy
+
+ int line_size = ((3*w+3)/4) * 4; // each line is aligned on a DWORD (4
bytes)
+ uchar *dib = new uchar[line_size*h]; // create temporary buffer to read DIB
+
+ // fill in bitmap info for GetDIBits
+
+ BITMAPINFO bi;
+ bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
+ bi.bmiHeader.biWidth = w;
+ bi.bmiHeader.biHeight = -h; // negative => top-down DIB
+ bi.bmiHeader.biPlanes = 1;
+ bi.bmiHeader.biBitCount = 24; // 24 bits RGB
+ bi.bmiHeader.biCompression = BI_RGB;
+ bi.bmiHeader.biSizeImage = 0;
+ bi.bmiHeader.biXPelsPerMeter = 0;
+ bi.bmiHeader.biYPelsPerMeter = 0;
+ bi.bmiHeader.biClrUsed = 0;
+ bi.bmiHeader.biClrImportant = 0;
+
+ // copy bitmap from original DC (Window, Fl_Offscreen, ...)
+
+ HDC hdc = CreateCompatibleDC(fl_gc);
+ HBITMAP hbm = CreateCompatibleBitmap(fl_gc,w,h);
+
+ int save_dc = SaveDC(hdc); // save context for cleanup
+ SelectObject(hdc,hbm); // select bitmap
+ BitBlt(hdc,0,0,w,h,fl_gc,X,Y,SRCCOPY); // copy image section to DDB
+
+ // copy RGB image data to the allocated DIB
+
+ GetDIBits(hdc, hbm, 0, h, dib, (BITMAPINFO *)&bi, DIB_RGB_COLORS);
+
+ // finally copy the image data to the user buffer
+
+ for (int j = 0; j<h; j++) {
+ const uchar *src = dib + j * line_size; // source line
+ uchar *tg = p + (j + shift_y) * d * ww + shift_x * d; // target line
+ for (int i = 0; i<w; i++) {
+ uchar b = *src++;
+ uchar g = *src++;
+ *tg++ = *src++; // R
+ *tg++ = g; // G
+ *tg++ = b; // B
+ if (alpha)
+ *tg++ = alpha; // alpha
}
}
+ // free used GDI and other structures
+
+ RestoreDC(hdc,save_dc); // reset DC
+ DeleteDC(hdc);
+ DeleteObject(hbm);
+ delete[] dib; // delete DIB temporary buffer
+
return p;
}
-
//
// End of "$Id$".
//
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