[英]Problem with SDL_DisplayFormatAlpha (c++)
As I stated in this question , I am using SDL for a small game I'm developing. 正如我在此问题中所述 ,我正在将SDL用于正在开发的小型游戏。 Now I am having problems with SDL_DisplayFormatAlpha. 现在,我在使用SDL_DisplayFormatAlpha时遇到问题。 I am trying to create a surface with an alpha channel from a PNG image. 我正在尝试从PNG图像创建具有alpha通道的表面。 It was working before, but now that I've done some slight refactoring something got broken. 它以前工作过,但是现在我做了一些轻微的重构,结果有些问题。 I've narrowed it down to this constructor: 我将其范围缩小到此构造函数:
Surface::Surface( tfilename file ) {
// initialize the surface data member to the image indicated by filename
SDL_Surface *tempSurface;
tempSurface = IMG_Load( file.c_str() );
if ( !tempSurface ) {
surface = NULL;
exit(1);
}
else {
surface = SDL_DisplayFormatAlpha( tempSurface );
//surface = tempSurface;
}
SDL_FreeSurface( tempSurface );
}
This compiles just fine, but when I run it I get a Segmentation fault. 这样编译就可以了,但是当我运行它时,出现了分段错误。 The error reported by gdb: gdb报告的错误:
Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0xb79c16c0 (LWP 8089)] 0xb7e8b9a3 in SDL_DisplayFormatAlpha () from /usr/lib/libSDL-1.2.so.0
The stack trace is as follows: 堆栈跟踪如下:
#0 0xb7e8b9a3 in SDL_DisplayFormatAlpha () from /usr/lib/libSDL-1.2.so.0 #1 0x0804987e in Surface (this=0x804d060, file=@0xbfb20760) at Surface.cpp:16 #2 0x0804a159 in Image (this=0x804d038, x=0, y=0, file=@0xbfb207a0) at Image.cpp:16 #3 0x0804a3de in Object (this=0x804d028, imageFile=@0xbfb207dc) at Object.cpp:4 #4 0x080491cb in Application (this=0xbfb20810) at Application.cpp:8 #5 0x08048e0d in main () at main.cpp:5
If I comment out surface = SDL_DisplayFormatAlpha( tempSurface );
如果我注释掉surface = SDL_DisplayFormatAlpha( tempSurface );
and SDL_FreeSurface( tempSurface );
和SDL_FreeSurface( tempSurface );
and uncomment surface = tempSurface;
和surface = tempSurface;
like so: 像这样:
Surface::Surface( tfilename file ) {
// initialize the surface data member to the image indicated by filename
SDL_Surface *tempSurface;
tempSurface = IMG_Load( file.c_str() );
if ( !tempSurface ) {
surface = NULL;
exit(1);
}
else {
//surface = SDL_DisplayFormatAlpha( tempSurface );
surface = tempSurface;
}
//SDL_FreeSurface( tempSurface );
}
Then it seems to work just fine. 然后,似乎工作正常。 Can anyone tell me what's going on? 谁能告诉我怎么回事? Actually, the transparency seems to work, too when I comment out SDL_DisplayFormatAlpha. 实际上,当我注释掉SDL_DisplayFormatAlpha时,透明度似乎也起作用。 Is that function only meant to be used with images that do not already have an alpha channel? 该功能仅适用于尚未具有Alpha通道的图像吗?
IMG_Load should handle transparent PNG's automatically, as the end of your post notes. IMG_Load应该自动处理透明的PNG,作为帖子的结尾。 What is the actual exception/error being thrown? 实际抛出的异常/错误是什么? Your stack trace doesn't show that. 您的堆栈跟踪没有显示出来。
If you read the link here (related function): 如果您在此处阅读链接(相关功能):
SDL_DisplayFormat SDL_DisplayFormat
"You have to call SDL_Init before using the SDL_DisplayFormat function. If you don't, your program will crash with an access violation." “使用SDL_DisplayFormat函数之前,您必须先调用SDL_Init。否则,您的程序将因访问冲突而崩溃。”
Could that be your problem? 那可能是你的问题吗?
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