Difference between revisions of "API-Truecolor"

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1,606 bytes added ,  08:06, 9 July 2009
→‎Example: Commented code better and added screenshot
(→‎Example: Commented code better and added screenshot)
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==== Example ====
==== Example ====
Here is an example of a simple engine that uses the best color depth available to display an RGB color-cycling gradient.
Here is an example of a simple engine that uses the best color depth available to display and color-cycle this gradient: [[Image:QuuxGradientRGB565.png]]
<syntax type="C++">
<syntax type="C++">
Common::Error QuuxEngine::run() {
Common::Error QuuxEngine::run() {
Graphics::PixelFormat format = _system->getSupportedFormats().front();
// Obtain the best possible format from the backend.
initGraphics(640, 480, true, &format);
Graphics::PixelFormat ourFormat = _system->getSupportedFormats().front();
 
// If our engine could only handle one format, we would specify it here instead of asking the backend:
// // RGB555
// Graphics::PixelFormat ourFormat(2, 3, 3, 3, 8, 10, 5, 0,  0);
 
// If our engine could handle only a few formats, this would look quite different:
//  Common::List<Graphics::PixelFormat> ourFormatList;
//
// // RGB555
// Graphics::PixelFormat ourFormat(2, 3, 3, 3, 8, 10, 5, 0,  0);
// ourFormatList.push_back(ourFormat);
//
// // XRGB1555
// ourFormat(2, 3, 3, 3, 7, 10, 5, 0, 15);
// ourFormatList.push_back(ourFormat);
//
// // Get the best format which is compatible between our engine and the backend
// ourFormat = Graphics::findCompatibleFormat(_system->getSupportedFormats(),ourFormatList);
 
// Attempt to initialize a 640 x 480 surface with that format
initGraphics(640, 480, true, &ourFormat);
 
// Use the format the system was able to provide
// in case it cannot support that format at our requested resolution
format = _system->getScreenFormat();
format = _system->getScreenFormat();


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if (format.bytesPerPixel == 1) {
if (format.bytesPerPixel == 1) {
// Initialize palette to simulate RGB332
// Initialize palette to simulate RGB332
// If our engine had no 256 color mode support, we would error out here:
//  return Common::kUnsupportedColorMode;
byte palette[1024];
byte palette[1024];
memset(&palette,0,1024);
memset(&palette,0,1024);
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while (!shouldQuit()) {
while (!shouldQuit()) {


// Draw the actual gradient
for (int16 y = 0; y < 480; y++) {
for (int16 y = 0; y < 480; y++) {
uint8 *dst = offscreenBuffer + (y * 640 * format.bytesPerPixel);
uint8 *dst = offscreenBuffer + (y * 640 * format.bytesPerPixel);
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t &= (format.bytesPerPixel << 3) - 1;
t &= (format.bytesPerPixel << 3) - 1;
color = (color << t) | (color >> ((format.bytesPerPixel << 3) - t));
color = (color << t) | (color >> ((format.bytesPerPixel << 3) - t));
// Currently we have to jump through hoops to write variable-length data in an endian-safe manner.
// In a real-life implementation, it would probably be better to have an if/else-if tree or
// a switch to determine the correct WRITE_UINT* function to use in the current bitdepth.
// Though, something like this might end up being necessary for 24-bit pixels, anyway.
#ifdef SCUMM_BIG_ENDIAN
#ifdef SCUMM_BIG_ENDIAN
for (int i = 0; i < format.bytesPerPixel; i++)
for (int i = 0; i < format.bytesPerPixel; i++)
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}
}
}
}
Common::Rect r;
r.top = 0;
r.left = 0;
r.bottom = 479;
r.right = 639;
_system->copyRectToScreen(offscreenBuffer, 640 * format.bytesPerPixel, 0, 0, 640, 480);
_system->copyRectToScreen(offscreenBuffer, 640 * format.bytesPerPixel, 0, 0, 640, 480);
_system->updateScreen();
_system->updateScreen();
parseEvents();
parseEvents();
// Wait a semi-arbitrary length in order to animate fluidly, but not insanely fast
_system->delayMillis(66);
_system->delayMillis(66);
t++;
t++;
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}
}
</syntax>
</syntax>
And a screenshot of it in action:


=== Backend initialization protocol ===
=== Backend initialization protocol ===
20

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