Mercurial > sdl-ios-xcode
annotate docs/html/sdlgetrgba.html @ 1259:36f24cdfcda7
te: Thu, 17 Apr 2003 11:25:26 -0700
From: "Jim"
Subject: [SDL] Frame buffer patches...
Would seem that GCC 3.2.2 promotes all signed values to unsigned if any single vlaue is unsigned in an expression...
for instance when calculating an elo touch position....evertyhign is an (int) except for cach_vinfo.xres which is unsigned. THerefore if y
ou reverse the SDL_ELO_MIN_X and SDL_ELO_MAX_X values the resulging negative value pegs the expression to it's max. Attached it the accumu
lated patch to typecast the unsigned values to (int)
- *dx = (cache_vinfo.xres - (cache_vinfo.xres * (input_x - ELO_MIN_X)) / width);
+ *dx = ((int)cache_vinfo.xres - ((int)cache_vinfo.xres * (input_x - ELO_MIN_X)) / width);
and also to provide quite failure to operations which have the screen currently locked...
The touch screen I'm using the original values were exactly opposite of any position I touched on the screen - evaluating the math the expr
ession SHOULD have handled reversing the min and max values - and after casting the unsigned .xres and .yres to a signed int - worked well.
..
Jim
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Tue, 24 Jan 2006 06:36:43 +0000 |
parents | 355632dca928 |
children |
rev | line source |
---|---|
0 | 1 <HTML |
2 ><HEAD | |
3 ><TITLE | |
4 >SDL_GetRGBA</TITLE | |
5 ><META | |
6 NAME="GENERATOR" | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ |
0 | 8 "><LINK |
9 REL="HOME" | |
10 TITLE="SDL Library Documentation" | |
11 HREF="index.html"><LINK | |
12 REL="UP" | |
13 TITLE="Video" | |
14 HREF="video.html"><LINK | |
15 REL="PREVIOUS" | |
16 TITLE="SDL_GetRGB" | |
17 HREF="sdlgetrgb.html"><LINK | |
18 REL="NEXT" | |
19 TITLE="SDL_CreateRGBSurface" | |
20 HREF="sdlcreatergbsurface.html"></HEAD | |
21 ><BODY | |
22 CLASS="REFENTRY" | |
23 BGCOLOR="#FFF8DC" | |
24 TEXT="#000000" | |
25 LINK="#0000ee" | |
26 VLINK="#551a8b" | |
27 ALINK="#ff0000" | |
28 ><DIV | |
29 CLASS="NAVHEADER" | |
30 ><TABLE | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
31 SUMMARY="Header navigation table" |
0 | 32 WIDTH="100%" |
33 BORDER="0" | |
34 CELLPADDING="0" | |
35 CELLSPACING="0" | |
36 ><TR | |
37 ><TH | |
38 COLSPAN="3" | |
39 ALIGN="center" | |
40 >SDL Library Documentation</TH | |
41 ></TR | |
42 ><TR | |
43 ><TD | |
44 WIDTH="10%" | |
45 ALIGN="left" | |
46 VALIGN="bottom" | |
47 ><A | |
48 HREF="sdlgetrgb.html" | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
49 ACCESSKEY="P" |
0 | 50 >Prev</A |
51 ></TD | |
52 ><TD | |
53 WIDTH="80%" | |
54 ALIGN="center" | |
55 VALIGN="bottom" | |
56 ></TD | |
57 ><TD | |
58 WIDTH="10%" | |
59 ALIGN="right" | |
60 VALIGN="bottom" | |
61 ><A | |
62 HREF="sdlcreatergbsurface.html" | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
63 ACCESSKEY="N" |
0 | 64 >Next</A |
65 ></TD | |
66 ></TR | |
67 ></TABLE | |
68 ><HR | |
69 ALIGN="LEFT" | |
70 WIDTH="100%"></DIV | |
71 ><H1 | |
72 ><A | |
73 NAME="SDLGETRGBA" | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
74 ></A |
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
75 >SDL_GetRGBA</H1 |
0 | 76 ><DIV |
77 CLASS="REFNAMEDIV" | |
78 ><A | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
79 NAME="AEN1747" |
0 | 80 ></A |
81 ><H2 | |
82 >Name</H2 | |
83 >SDL_GetRGBA -- Get RGBA values from a pixel in the specified pixel format.</DIV | |
84 ><DIV | |
85 CLASS="REFSYNOPSISDIV" | |
86 ><A | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
87 NAME="AEN1750" |
0 | 88 ></A |
89 ><H2 | |
90 >Synopsis</H2 | |
91 ><DIV | |
92 CLASS="FUNCSYNOPSIS" | |
93 ><A | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
94 NAME="AEN1751" |
0 | 95 ></A |
96 ><P | |
97 ></P | |
98 ><PRE | |
99 CLASS="FUNCSYNOPSISINFO" | |
100 >#include "SDL.h"</PRE | |
101 ><P | |
102 ><CODE | |
103 ><CODE | |
104 CLASS="FUNCDEF" | |
105 >void <B | |
106 CLASS="FSFUNC" | |
107 >SDL_GetRGBA</B | |
108 ></CODE | |
109 >(Uint32 pixel, SDL_PixelFormat *fmt, Uint8 *r, Uint8 *g, Uint8 *b, Uint8 *a);</CODE | |
110 ></P | |
111 ><P | |
112 ></P | |
113 ></DIV | |
114 ></DIV | |
115 ><DIV | |
116 CLASS="REFSECT1" | |
117 ><A | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
118 NAME="AEN1757" |
0 | 119 ></A |
120 ><H2 | |
121 >Description</H2 | |
122 ><P | |
123 >Get RGBA component values from a pixel stored in the specified pixel format.</P | |
124 ><P | |
125 >This function uses the entire 8-bit [0..255] range when converting color | |
126 components from pixel formats with less than 8-bits per RGB component | |
127 (e.g., a completely white pixel in 16-bit RGB565 format would return | |
128 [0xff, 0xff, 0xff] not [0xf8, 0xfc, 0xf8]).</P | |
129 ><P | |
130 >If the surface has no alpha component, the alpha will be returned as 0xff | |
131 (100% opaque).</P | |
132 ></DIV | |
133 ><DIV | |
134 CLASS="REFSECT1" | |
135 ><A | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
136 NAME="AEN1762" |
0 | 137 ></A |
138 ><H2 | |
139 >See Also</H2 | |
140 ><P | |
141 ><A | |
142 HREF="sdlgetrgb.html" | |
143 >SDL_GetRGB</A | |
144 >, | |
145 <A | |
146 HREF="sdlmaprgb.html" | |
147 >SDL_MapRGB</A | |
148 >, | |
149 <A | |
150 HREF="sdlmaprgba.html" | |
151 >SDL_MapRGBA</A | |
152 >, | |
153 <A | |
154 HREF="sdlpixelformat.html" | |
155 >SDL_PixelFormat</A | |
156 ></P | |
157 ></DIV | |
158 ><DIV | |
159 CLASS="NAVFOOTER" | |
160 ><HR | |
161 ALIGN="LEFT" | |
162 WIDTH="100%"><TABLE | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
163 SUMMARY="Footer navigation table" |
0 | 164 WIDTH="100%" |
165 BORDER="0" | |
166 CELLPADDING="0" | |
167 CELLSPACING="0" | |
168 ><TR | |
169 ><TD | |
170 WIDTH="33%" | |
171 ALIGN="left" | |
172 VALIGN="top" | |
173 ><A | |
174 HREF="sdlgetrgb.html" | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
175 ACCESSKEY="P" |
0 | 176 >Prev</A |
177 ></TD | |
178 ><TD | |
179 WIDTH="34%" | |
180 ALIGN="center" | |
181 VALIGN="top" | |
182 ><A | |
183 HREF="index.html" | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
184 ACCESSKEY="H" |
0 | 185 >Home</A |
186 ></TD | |
187 ><TD | |
188 WIDTH="33%" | |
189 ALIGN="right" | |
190 VALIGN="top" | |
191 ><A | |
192 HREF="sdlcreatergbsurface.html" | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
193 ACCESSKEY="N" |
0 | 194 >Next</A |
195 ></TD | |
196 ></TR | |
197 ><TR | |
198 ><TD | |
199 WIDTH="33%" | |
200 ALIGN="left" | |
201 VALIGN="top" | |
202 >SDL_GetRGB</TD | |
203 ><TD | |
204 WIDTH="34%" | |
205 ALIGN="center" | |
206 VALIGN="top" | |
207 ><A | |
208 HREF="video.html" | |
803
355632dca928
Updated SDL HTML documentation
Sam Lantinga <slouken@libsdl.org>
parents:
181
diff
changeset
|
209 ACCESSKEY="U" |
0 | 210 >Up</A |
211 ></TD | |
212 ><TD | |
213 WIDTH="33%" | |
214 ALIGN="right" | |
215 VALIGN="top" | |
216 >SDL_CreateRGBSurface</TD | |
217 ></TR | |
218 ></TABLE | |
219 ></DIV | |
220 ></BODY | |
221 ></HTML | |
222 > |