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Hi, with the function SDL_SaveBMP I can save a image from a Surface exists a function that allows me save a image from a Render. I need do a ScreenShoot.

Thanks!

Hello there,

AFAIK, SDL2 does not have a public function available to do this for us
magically -- perhaps because it is so high-level (app-level / specific) -- but that's fine, because we can do it ourselves easily using the SDL2 Renderer
API (save to use with OpenGL, even).

// Psuedo-code for saving a screen shot of your SDL_Window contents; sloppily
copied from my game engine, nomlib, nom::RenderWindow && nom::Renderer class interfaces @ https://github.com/i8degrees/nomlib
{
SDL_Rect clip;
void* pixels = nullptr;

SDL_Rect output_size; // width & height in pixels

if( SDL_GetRendererOutputSize ( this->renderer(), &output_size.w, &output_size.h ) != 0 )
{
NOM_LOG_ERR( NOM, SDL_GetError() );
return Size2i::null;
}

// In order to accurately capture our window, with respect to aspect ratio,
// such as the case of us using device independent scaling [1], we must
// calculate the true bounding dimensions of our rendering target.
clip.x = 0;
clip.y = 0;
clip.w = output_size.w;
clip.h = output_size.h;

pixels = static_cast<uint32*> ( malloc( clip.w * clip.h * 4 ) );

if ( SDL_RenderReadPixels( this->renderer(),
// Use calculated bounding dimensions;
// Pass null to dump the pixels of the entire
// render target
&clip,
// Use the most optimal pixel format;
// Pass zero here to obtain the pixel format of
// the render target
// Either use a filled RenderInfo struct to obtain
// optimal texture format,
// ...or... cheat! in the mean time and use this
SDL_PIXELFORMAT_ARGB8888,
// Allocated pointer to be filled in with pixels
// from render target
pixels,
// Pitch of our pixels pointer
clip.w * 4 ) != 0 )
{
NOM_LOG_ERR( NOM, SDL_GetError() );
return nullptr;
}

int bpp = 0; // bits per pixel
uint32 red_mask = 0;
uint32 green_mask = 0;
uint32 blue_mask = 0;
uint32 alpha_mask = 0;

RendererInfo caps = this->caps(); // Pixel format
Image screenshot; // SDL_Surface*

// Width & height of target in pixels
SDL_Rect render_size = output_size;

if ( SDL_BOOL( SDL_PixelFormatEnumToMasks ( caps.optimal_texture_format(), &bpp, &red_mask, &green_mask, &blue_mask, &alpha_mask ) ) != true )
{
NOM_LOG_ERR( NOM, SDL_GetError() );
return false;
}

screenshot.initialize( pixels, renderer_size.w, renderer_size.h, bpp, (renderer_size.w * 4), red_mask, green_mask, blue_mask, alpha_mask );

// This is a C++ wrapper for ( pixels, width, height, bits_per_pixel, pitch, Rmask, Gmask, Bmask, Amask )

// Note that you may also use SDL_SavePNG & friends here, too!
if( SDL_SaveBMP( screenshot(), "screenshot.bmp" ) != 0 )
{
// Handle err
}

// Success!
// NOM_LOG_INFO( NOM, "The screen-shot file is saved at: ", filename );
}

Let me know if you have any questions. Good luck!

Cheers,
Jeffrey Carpenter

On 2014/10/ 02, at 7:49, alejandroicom wrote:


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Here´s a short function that creates a screenshot file (*.bmp) from a renderer. Hope it works the way you want.

Code:

If you use Software Renderer than this can probably work. There is no way to get pixel data from textures, unfortunately. Software Renderer however, uses a SDL_Surface, which you can directly pass to SDL_SaveBMP().

Pallav Nawani
IronCode Gaming Private Limited
Website: http://www.ironcode.com
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Mobile: 9997478768


On Thu, Oct 2, 2014 at 6:19 PM, alejandroicom wrote:

Works fine! thanks!