Mercurial > sdl-ios-xcode
annotate docs/man3/SDL_PixelFormat.3 @ 3100:7dc982143c06
Date: Sun, 22 Mar 2009 12:52:29 +0000
From: Luke Benstead
Subject: OpenGL 3.0 Context Creation
I've attached a patch which implements OpenGL 3.x context creation on
the latest SVN. I've added two options to SDL_GL_SetAttribute, these
are SDL_GL_CONTEXT_MAJOR_VERSION and SDL_GL_CONTEXT_MINOR_VERSION.
These default to 2 and 1 respectively. If the major version is less
than 3 then the current context creation method is used, otherwise the
appropriate new context creation function is called (depending on the
platform).
Sample code:
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
printf("Unable to initialize SDL: %s\n", SDL_GetError());
return 1;
}
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); //Without these 2 lines, SDL will create a GL 2.x context
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_Surface* screen = SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL | SDL_FULLSCREEN );
I've implemented context creation on both Win32 and X and run basic
tests on both. This patch doesn't provide access to all the options
allowed by the new context creation (e.g. shared contexts, forward
compatible contexts) but they can be added pretty easily.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Tue, 24 Mar 2009 10:43:53 +0000 |
| parents | 546f7c1eb755 |
| children | 1238da4a7112 |
| rev | line source |
|---|---|
|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
1 .TH "SDL_PixelFormat" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" |
| 0 | 2 .SH "NAME" |
|
2283
546f7c1eb755
Merged revision 3472 from SDL 1.2, fixing bug #493
Sam Lantinga <slouken@libsdl.org>
parents:
1279
diff
changeset
|
3 SDL_PixelFormat \- Stores surface format information |
| 0 | 4 .SH "STRUCTURE DEFINITION" |
| 5 .PP | |
| 6 .nf | |
|
1279
e867f327aa54
*** empty log message ***
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
7 \f(CWtypedef struct SDL_PixelFormat { |
| 0 | 8 SDL_Palette *palette; |
| 9 Uint8 BitsPerPixel; | |
| 10 Uint8 BytesPerPixel; | |
|
1279
e867f327aa54
*** empty log message ***
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
11 Uint8 Rloss, Gloss, Bloss, Aloss; |
| 0 | 12 Uint8 Rshift, Gshift, Bshift, Ashift; |
|
1279
e867f327aa54
*** empty log message ***
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
13 Uint32 Rmask, Gmask, Bmask, Amask; |
| 0 | 14 Uint32 colorkey; |
| 15 Uint8 alpha; | |
| 16 } SDL_PixelFormat;\fR | |
| 17 .fi | |
| 18 .PP | |
| 19 .SH "STRUCTURE DATA" | |
| 20 .TP 20 | |
| 21 \fBpalette\fR | |
| 22 Pointer to the \fIpalette\fR, or \fBNULL\fP if the \fBBitsPerPixel\fR>8 | |
| 23 .TP 20 | |
| 24 \fBBitsPerPixel\fR | |
| 25 The number of bits used to represent each pixel in a surface\&. Usually 8, 16, 24 or 32\&. | |
| 26 .TP 20 | |
| 27 \fBBytesPerPixel\fR | |
| 28 The number of bytes used to represent each pixel in a surface\&. Usually one to four\&. | |
| 29 .TP 20 | |
| 30 \fB[RGBA]mask\fR | |
| 31 Binary mask used to retrieve individual color values | |
| 32 .TP 20 | |
| 33 \fB[RGBA]loss\fR | |
| 34 Precision loss of each color component (2^[RGBA]loss) | |
| 35 .TP 20 | |
| 36 \fB[RGBA]shift\fR | |
| 37 Binary left shift of each color component in the pixel value | |
| 38 .TP 20 | |
| 39 \fBcolorkey\fR | |
| 40 Pixel value of transparent pixels | |
| 41 .TP 20 | |
| 42 \fBalpha\fR | |
| 43 Overall surface alpha value | |
| 44 .SH "DESCRIPTION" | |
| 45 .PP | |
| 46 A \fBSDL_PixelFormat\fR describes the format of the pixel data stored at the \fBpixels\fR field of a \fI\fBSDL_Surface\fR\fR\&. Every surface stores a \fBSDL_PixelFormat\fR in the \fBformat\fR field\&. | |
| 47 .PP | |
| 48 If you wish to do pixel level modifications on a surface, then understanding how SDL stores its color information is essential\&. | |
| 49 .PP | |
| 50 8-bit pixel formats are the easiest to understand\&. Since its an 8-bit format, we have 8 \fBBitsPerPixel\fR and 1 \fBBytesPerPixel\fR\&. Since \fBBytesPerPixel\fR is 1, all pixels are represented by a Uint8 which contains an index into \fBpalette\fR->\fBcolors\fR\&. So, to determine the color of a pixel in a 8-bit surface: we read the color index from \fBsurface\fR->\fBpixels\fR and we use that index to read the \fI\fBSDL_Color\fR\fR structure from \fBsurface\fR->\fBformat\fR->\fBpalette\fR->\fBcolors\fR\&. Like so: | |
| 51 .PP | |
| 52 .nf | |
| 53 \f(CWSDL_Surface *surface; | |
| 54 SDL_PixelFormat *fmt; | |
| 55 SDL_Color *color; | |
| 56 Uint8 index; | |
| 57 | |
| 58 \&. | |
| 59 \&. | |
| 60 | |
| 61 /* Create surface */ | |
| 62 \&. | |
| 63 \&. | |
| 64 fmt=surface->format; | |
| 65 | |
| 66 /* Check the bitdepth of the surface */ | |
| 67 if(fmt->BitsPerPixel!=8){ | |
| 68 fprintf(stderr, "Not an 8-bit surface\&. | |
| 69 "); | |
| 70 return(-1); | |
| 71 } | |
| 72 | |
| 73 /* Lock the surface */ | |
| 74 SDL_LockSurface(surface); | |
| 75 | |
| 76 /* Get the topleft pixel */ | |
| 77 index=*(Uint8 *)surface->pixels; | |
| 78 color=fmt->palette->colors[index]; | |
| 79 | |
| 80 /* Unlock the surface */ | |
| 81 SDL_UnlockSurface(surface); | |
| 82 printf("Pixel Color-> Red: %d, Green: %d, Blue: %d\&. Index: %d | |
| 83 ", | |
| 84 color->r, color->g, color->b, index); | |
| 85 \&. | |
| 86 \&.\fR | |
| 87 .fi | |
| 88 .PP | |
| 89 .PP | |
|
55
55f1f1b3e27d
Added new docs for SDL 1.2.1
Sam Lantinga <slouken@lokigames.com>
parents:
0
diff
changeset
|
90 Pixel formats above 8-bit are an entirely different experience\&. They are considered to be "TrueColor" formats and the color information is stored in the pixels themselves, not in a palette\&. The mask, shift and loss fields tell us how the color information is encoded\&. The mask fields allow us to isolate each color component, the shift fields tell us the number of bits to the right of each component in the pixel value and the loss fields tell us the number of bits lost from each component when packing 8-bit color component in a pixel\&. |
| 0 | 91 .PP |
| 92 .nf | |
| 93 \f(CW/* Extracting color components from a 32-bit color value */ | |
| 94 SDL_PixelFormat *fmt; | |
| 95 SDL_Surface *surface; | |
| 96 Uint32 temp, pixel; | |
| 97 Uint8 red, green, blue, alpha; | |
| 98 \&. | |
| 99 \&. | |
| 100 \&. | |
| 101 fmt=surface->format; | |
| 102 SDL_LockSurface(surface); | |
|
55
55f1f1b3e27d
Added new docs for SDL 1.2.1
Sam Lantinga <slouken@lokigames.com>
parents:
0
diff
changeset
|
103 pixel=*((Uint32*)surface->pixels); |
| 0 | 104 SDL_UnlockSurface(surface); |
| 105 | |
| 106 /* Get Red component */ | |
| 107 temp=pixel&fmt->Rmask; /* Isolate red component */ | |
| 108 temp=temp>>fmt->Rshift;/* Shift it down to 8-bit */ | |
| 109 temp=temp<<fmt->Rloss; /* Expand to a full 8-bit number */ | |
| 110 red=(Uint8)temp; | |
| 111 | |
| 112 /* Get Green component */ | |
| 113 temp=pixel&fmt->Gmask; /* Isolate green component */ | |
| 114 temp=temp>>fmt->Gshift;/* Shift it down to 8-bit */ | |
| 115 temp=temp<<fmt->Gloss; /* Expand to a full 8-bit number */ | |
| 116 green=(Uint8)temp; | |
| 117 | |
| 118 /* Get Blue component */ | |
| 119 temp=pixel&fmt->Bmask; /* Isolate blue component */ | |
| 120 temp=temp>>fmt->Bshift;/* Shift it down to 8-bit */ | |
| 121 temp=temp<<fmt->Bloss; /* Expand to a full 8-bit number */ | |
| 122 blue=(Uint8)temp; | |
| 123 | |
| 124 /* Get Alpha component */ | |
| 125 temp=pixel&fmt->Amask; /* Isolate alpha component */ | |
| 126 temp=temp>>fmt->Ashift;/* Shift it down to 8-bit */ | |
| 127 temp=temp<<fmt->Aloss; /* Expand to a full 8-bit number */ | |
| 128 alpha=(Uint8)temp; | |
| 129 | |
| 130 printf("Pixel Color -> R: %d, G: %d, B: %d, A: %d | |
| 131 ", red, green, blue, alpha); | |
| 132 \&. | |
| 133 \&. | |
| 134 \&.\fR | |
| 135 .fi | |
| 136 .PP | |
| 137 .SH "SEE ALSO" | |
| 138 .PP | |
| 139 \fI\fBSDL_Surface\fR\fR, \fI\fBSDL_MapRGB\fP\fR | |
|
181
e5bc29de3f0a
Updated from the SDL Documentation Project
Sam Lantinga <slouken@libsdl.org>
parents:
55
diff
changeset
|
140 ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01 |