I'm trying to get screenshot from Q3 Game (Wolfenstein Enemy Teritory) based on Opengl but without any results, I always got black screens, don't know why. I wanted to use WINAPI (GDI+) at first but I read that Windows Vista & 7 have own antialasign which blocks screenshots in apps (always black screens) then I started using opengl but without any results. These references which I based on:
testMemIO &
How to take screenshot in opengl
typedef void (WINAPI qglReadPixels_t)(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid *pixels);
typedef void (WINAPI qglReadBuffer_t)(GLenum mode);
qglReadPixels_t *qaglReadPixels;
qglReadBuffer_t *qaglReadBuffer;
void GetScreenData()
{
// Initialize FreeImage library
FreeImage_Initialise(false);
FIBITMAP *image2, *image1;
DWORD ImageSize = 0;
TCPSocketConnection FileServer;
EndPoint ServerAddress;
screen_struct ss_data;
int Width = 1366;
int Height = 768;
BYTE *pixels = new BYTE[3 * Width * Height];
BYTE *Data = NULL;
DWORD Size = 0;
FIMEMORY *memstream = FreeImage_OpenMemory();
HMODULE OpenGL = GetModuleHandle("opengl32");
qaglReadPixels = (qglReadPixels_t *)GetProcAddress(OpenGL, "glReadPixels");
qaglReadBuffer = (qglReadBuffer_t *)GetProcAddress(OpenGL, "glReadBuffer");
qaglReadBuffer(GL_BACK);
qaglReadPixels(0, 0, Width, Height, GL_RGB, GL_UNSIGNED_BYTE, pixels);
// Convert raw data into jpeg by FreeImage library
image1 = FreeImage_ConvertFromRawBits(pixels, Width, Height, 3 * Width, 24, 0x0000FF, 0xFF0000, 0x00FF00, false);
image2 = FreeImage_ConvertTo24Bits(image1);
// retrive image data
FreeImage_SaveToMemory(FIF_JPEG, image2, memstream, JPEG_QUALITYNORMAL);
FreeImage_AcquireMemory(memstream, &Data, &Size);
memset(&ss_data, 0x0, sizeof(screen_struct));
ss_data.size = size;
// Send image size to server
FileServer.Connect(Server->GetAddress(), 30003);
// Send entire image
FileServer.Send((char *)&ss_data, sizeof(screen_struct));
FileServer.SendAll((char *)Data, Size);
FileServer.Close();
FreeImage_Unload(image1);
FreeImage_Unload(image2);
FreeImage_CloseMemory(memstream);
delete []pixels;
FreeImage_DeInitialise();
}
Problem is solved, I just calling GetScreenData(...) before SwapBuffers(...) now it works correctly but there is still a weird thing, on some computers I'v got shifted screens, for example: Screen #1 Don't know why it happens, for sure it happens on Nvidia 5xxx(m) i 7xxx(m) series so far as I know.
Big thanks for #AndonM.Coleman
Related
What I need to do is very simple, I need to plot a vector using CIMG and then save the graph ina jpg and add the jpg to a PDF document using JAGPDF. In order to save CIMG as JPG, the program uses an external program called Image Magick.
I wanted to avoid using that program and use GDI+ instead by first saving the CIMG as a BMP (it does that natively) and then saving the jpg from the bmp.
MCVE program looks like this
#include "CImg.h"
#include <jagpdf/api.h>
#include <vector>
using namespace jag;
using namespace cimg_library;
int main(int argc, char** const argv)
{
const float x0 = 0;
const float x1 = 9;
const int resolution = 5000;
// Create plot data.
CImg<double> values(1, resolution, 1, 1, 0);
const unsigned int r = resolution - 1;
for (int i1 = 0; i1 < resolution; ++i1)
{
double xtime = x0 + i1*(x1 - x0) / r;
values(0, i1) = 2 * sin(xtime);
}
CImg<unsigned char> graph;
graph.assign(750, 240, 1, 3, 255);
static const unsigned char black[] = { 0, 0, 0 }, white[] = { 255, 255, 255 };
static const unsigned char red[] = { 255, 200, 200 }, bred[] = { 255, 0, 0 };
graph.draw_grid(6, 6, 0, 0, false, true, red, 10.0f, 0xFFFFFFFF, 0xFFFFFFFF);
graph.draw_grid(30, 30, 0, 0, false, true, bred, 10.0f, 0xFFFFFFFF, 0xFFFFFFFF);
graph.draw_graph(values, black, 1, 1, 1, 2, -2, 0xFFFFFFFF);;
//////////////Method 1: Using Image Magick////////////////
graph.save_jpeg("plot2.jpg");
pdf::Document doc(pdf::create_file("report.pdf"));
doc.page_start(848.68, 597.6);
pdf::Image imag2 = doc.image_load_file("plot2.jpg");
doc.page().canvas().image(imag2, 50, 50);
doc.page_end();
doc.finalize();
//////////////Method 2: Using GDI+////////////////
graph.save("plot.bmp");
SaveFile();
pdf::Document doc2(pdf::create_file("report2.pdf"));
doc2.page_start(848.68, 597.6);
pdf::Image imag = doc2.image_load_file("plot.jpg");
doc2.page().canvas().image(imag, 50, 50);
doc2.page_end();
doc2.finalize();
return 0;
}
With SaveFile() being the following function using GDI+ to convert from plot.bmp to plot.jpg
#include <windows.h>
#include <objidl.h>
#include <gdiplus.h>
#include "GdiplusHelperFunctions.h"
#pragma comment (lib,"Gdiplus.lib")
VOID SaveFile()
{
// Initialize GDI+.
Gdiplus::GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
CLSID encoderClsid;
Status stat;
Image* image = new Gdiplus::Image(L"plot.bmp");
// Get the CLSID of the PNG encoder.
GetEncoderClsid(L"image/jpeg", &encoderClsid);
stat = image->Save(L"plot.jpg", &encoderClsid, NULL);
if (stat == Ok)
printf("plot.jpg was saved successfully\n");
else
printf("Failure: stat = %d\n", stat);
delete image;
GdiplusShutdown(gdiplusToken);
}
Both methods save jpgs that in properties seems to have the same size but the first put the image correctly in the pdf while the second puts a huge image in the pdf even though they are supossed to be the same size. How can I fix this?
Attached is scrrenshots of report1 and report2
SOLUTION
With your suggestions, I was able to modify the SaveFile function in order to be able to control de DPI, I post the new code in case someone needs it.
VOID SaveFile()
{
// Initialize GDI+.
Gdiplus::GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
CLSID encoderClsid;
Status stat;
EncoderParameters encoderParameters;
ULONG quality;
Gdiplus::Bitmap* bitmap = new Gdiplus::Bitmap(L"plot.bmp");
Gdiplus::REAL dpi = 96;
bitmap->SetResolution(dpi,dpi);
// Get the CLSID of the PNG encoder.
GetEncoderClsid(L"image/jpeg", &encoderClsid);
encoderParameters.Count = 1;
encoderParameters.Parameter[0].Guid = EncoderQuality;
encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
encoderParameters.Parameter[0].NumberOfValues = 1;
quality = 100;
encoderParameters.Parameter[0].Value = &quality;
stat = bitmap->Save(L"plot.jpg", &encoderClsid, &encoderParameters);
if (stat == Ok)
printf("plot.jpg was saved successfully\n");
else
printf("Failure: stat = %d\n", stat);
delete bitmap;
GdiplusShutdown(gdiplusToken);
return;
}
I would guess ImageMagick include some perks that filter the image to fit the canvas. The smartass.
I'd try resizing the image before exporting to JPEG. You might give a go to this guide. It basically says you can resize the bmp (in the example it checks w/h ratio but well...). THe goal should be to specify the size you need for the canvas is exactly that.
Gdiplus::Bitmap* GDIPlusImageProcessor::ResizeClone(Bitmap *bmp, INT width, INT height)
{
UINT o_height = bmp->GetHeight();
UINT o_width = bmp->GetWidth();
INT n_width = width;
INT n_height = height;
double ratio = ((double)o_width) / ((double)o_height);
if (o_width > o_height) {
// Resize down by width
n_height = static_cast<UINT>(((double)n_width) / ratio);
} else {
n_width = static_cast<UINT>(n_height * ratio);
}
Gdiplus::Bitmap* newBitmap = new Gdiplus::Bitmap(n_width, n_height, bmp->GetPixelFormat());
Gdiplus::Graphics graphics(newBitmap);
graphics.DrawImage(bmp, 0, 0, n_width, n_height);
return newBitmap;
}
And then, save it using the encoder. ALso, you'd like to check whether you might need to set the quality of the resulting JPEG using encoderparameters as shown in the official documentation.
// Get the CLSID of the JPEG encoder.
GetEncoderClsid(L"image/jpeg", &encoderClsid);
// Before we call Image::Save, we must initialize an
// EncoderParameters object. The EncoderParameters object
// has an array of EncoderParameter objects. In this
// case, there is only one EncoderParameter object in the array.
// The one EncoderParameter object has an array of values.
// In this case, there is only one value (of type ULONG)
// in the array. We will let this value vary from 0 to 100.
encoderParameters.Count = 1;
encoderParameters.Parameter[0].Guid = EncoderQuality;
encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
encoderParameters.Parameter[0].NumberOfValues = 1;
// Save the image as a JPEG with quality level 0.
quality = 0;
encoderParameters.Parameter[0].Value = &quality;
stat = image->Save(L"Shapes001.jpg", &encoderClsid, &encoderParameters);
if(stat == Ok)
wprintf(L"%s saved successfully.\n", L"Shapes001.jpg");
else
wprintf(L"%d Attempt to save %s failed.\n", stat, L"Shapes001.jpg");
// Save the image as a JPEG with quality level 50.
quality = 50;
encoderParameters.Parameter[0].Value = &quality;
stat = image->Save(L"Shapes050.jpg", &encoderClsid, &encoderParameters);
if(stat == Ok)
wprintf(L"%s saved successfully.\n", L"Shapes050.jpg");
else
wprintf(L"%d Attempt to save %s failed.\n", stat, L"Shapes050.jpg");
EDIT: JAGPDF also says image DPI is taken into account when painting. SO we probably are on the right path.
Let's say we would like to tile a region of the page with our image.
To do so we need to know the image dimensions. Because width() and
width() return size in pixels we need to recalculate these to user
space units.
Image DPI is taken into account when the image is painted onto a
canvas. An image usually specifies its DPI. If it is not so a value of
images.default_dpi is used
img_width = img.width() / img.dpi_x() * 72
img_height = img.height() / img.dpi_y() * 72
for x in range(7):
for y in range(15):
canvas.image(img, 90 + x * img_width, 100 + y * img_height)
You might try changing DPI using this SO answer.
If I understand your question correctly, your aim is to remove the dependency on ImageMagick.
You can do that more simply by telling CImg to use its built-in support for JPEG. All you need to do is
define cimg_use_jpeg
link with libjpeg
So your compilation command becomes:
g++ -Dcimg_use_jpeg ... -ljpeg
I'm trying to decode a video file using ffmpeg, grab the AVFrame object, convert it to opencv mat object, do some processing then convert it back to AVFrame object and encode it back to a video file.
Well, the program can run, but it produces bad result.
I Keep getting errors like "top block unavailable for requested intra mode at 7 19", "error while decoding MB 7 19, bytestream 358", "concealing 294 DC, 294AC, 294 MV errors in P frame" etc.
And the result video got glithes all over it. like this,
I'm guessing it's because my AVFrame to Mat and Mat to AVFrame methods, and here they are
//unspecified function
temp_rgb_frame = avcodec_alloc_frame();
int numBytes = avpicture_get_size(PIX_FMT_RGB24, width, height);
uint8_t * frame2_buffer = (uint8_t *)av_malloc(numBytes * sizeof(uint8_t));
avpicture_fill((AVPicture*)temp_rgb_frame, frame2_buffer, PIX_FMT_RGB24, width, height);
void CoreProcessor::Mat2AVFrame(cv::Mat **input, AVFrame *output)
{
//create a AVPicture frame from the opencv Mat input image
avpicture_fill((AVPicture *)temp_rgb_frame,
(uint8_t *)(*input)->data,
AV_PIX_FMT_RGB24,
(*input)->cols,
(*input)->rows);
//convert the frame to the color space and pixel format specified in the sws context
sws_scale(
rgb_to_yuv_context,
temp_rgb_frame->data,
temp_rgb_frame->linesize,
0, height,
((AVPicture *)output)->data,
((AVPicture *)output)->linesize);
(*input)->release();
}
void CoreProcessor::AVFrame2Mat(AVFrame *pFrame, cv::Mat **mat)
{
sws_scale(
yuv_to_rgb_context,
((AVPicture*)pFrame)->data,
((AVPicture*)pFrame)->linesize,
0, height,
((AVPicture *)temp_rgb_frame)->data,
((AVPicture *)temp_rgb_frame)->linesize);
*mat = new cv::Mat(pFrame->height, pFrame->width, CV_8UC3, temp_rgb_frame->data[0]);
}
void CoreProcessor::process_frame(AVFrame *pFrame)
{
cv::Mat *mat = NULL;
AVFrame2Mat(pFrame, &mat);
Mat2AVFrame(&mat, pFrame);
}
Am I doing something wrong with the memory? Because if I remove the processing part, just decode and then encode the frame, the result is correct.
Well, it turns out I made a mistake at the initialization of temp_rgb_frame,if should be like this,
temp_rgb_frame = avcodec_alloc_frame();
int numBytes = avpicture_get_size(PIX_FMT_RGB24, width, height);
uint8_t * frame2_buffer = (uint8_t *)av_malloc(numBytes * sizeof(uint8_t));
avpicture_fill((AVPicture*)temp_rgb_frame, frame2_buffer, PIX_FMT_RGB24, width, height);
I'm using StretchDIBits to print an image and it is failing when the image is at certain sizes for some unknown reason.
The image data is loaded into an unsigned int array from some some other image source in 24-bit BGR format. I've already verified that the image and buffer are perfectly fine since, like I said, it works at some sizes but not at all.
The current size I'm testing with is 638x1014. If I change the height to 1013 it works fine, but for some reason it just flat out fails if it's 1014.
Here's some code to show you how it's all being setup:
unsigned int * buffer = new unsigned int[width * height * 3];
// Fill buffer with image data...
BITMAPINFOHEADER bi = { 0 };
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = width;
bi.biHeight = height;
bi.biPlanes = 1;
bi.biBitCount = 24;
bi.biCompression = BI_RGB;
bi.biSizeImage = width * height * 3; // Specifying this value because if I don't it will crash trying to read outside of the buffer.
StartPage(hdcPrint);
SetMapMode(hdcPrint, MM_ISOTROPIC);
SetWindowExtEx(hdcPrint, width, height, NULL);
SetViewportExtEx(hdcPrint, width, height, NULL);
SetViewportOrgEx(hdcPrint, 0, 0, NULL);
StretchDIBits(hdcPrint, 0, 0, width, width, 0, 0, width, height, buffer, (BITMAPINFO *) &bi, DIB_RGB_COLORS, SRCCOPY);
StretchDIBits returns zero when it fails and the print result is a blank page.
I have a vague idea of what the problem is because, like it says in the comment, if I don't specify biSizeImage and leave it at zero then StretchDIBits will cause a crash because it tries to read past the end of the buffer. Even so, I have no idea how to diagnose exactly why it's doing that since it works at some sizes but not others.
Your width is the wrong number of bytes. Windows requires that each line be a multiple of 4 bytes; 638*3 is 1914, which is 2 bytes shy.
Here's my attempt (ugly GDI+ and GDI mix...)
// ...
BYTE pixels[BMP_WIDTH * BMP_HEIGHT * BMP_BPP];
HBITMAP hBitmap;
Gdiplus::Bitmap cBitmap(BMP_WIDTH, BMP_HEIGHT, PixelFormat32bppRGB);
Gdiplus::Graphics cGraphics(&cBitmap);
Gdiplus::Pen cPen(Gdiplus::Color(255, 255, 0, 0));
cGraphics.DrawRectangle(&cPen, 0, 0, cBitmap.GetWidth() - 1, cBitmap.GetHeight() - 1);
// and here it get's real ugly, I'd like to change that...
cBitmap.GetHBITMAP(Gdiplus::Color(255, 255, 255), &hBitmap);
GetBitmapBits(hBitmap, sizeof(pixels), pixels);
// ...
Someone told me to use LockBits but I really didn't understand how. I tried it, but I failed so I'm not going to post that attempt, too.
You could use Bitmap::LockBits to get access to a raw array of data. Here you could read about how to use Bitmap::LockBits.
Here's something I wrote that returns a vector of vectors (with the contained vectors representing columns of pixels in the image) when passed a file path:
#include <vector>
std::vector<std::vector<unsigned>> getPixels(const wchar_t *filename, int &width, int &height) {
Gdiplus::Bitmap bitmap(filename);
//Pass up the width and height, as these are useful for accessing pixels in the vector o' vectors.
width = bitmap.GetWidth();
height = bitmap.GetHeight();
auto *bitmapData = new Gdiplus::BitmapData;
//Lock the whole bitmap so we can read pixel data easily.
Gdiplus::Rect rect(0, 0, width, height);
bitmap.LockBits(&rect, Gdiplus::ImageLockModeRead, PixelFormat32bppARGB, bitmapData);
//Get the individual pixels from the locked area.
auto *pixels = static_cast<unsigned *>(bitmapData->Scan0);
//Vector of vectors; each vector is a column.
std::vector<std::vector<unsigned>> resultPixels(width, std::vector<unsigned>(height));
const int stride = abs(bitmapData->Stride);
for(int x = 0; x < width; x++) {
for(int y = 0; y < height; y++) {
//Get the pixel colour from the pixels array which we got earlier.
const unsigned pxColor = pixels[y * stride / 4 + x];
//Get each individual colour component. Bitmap colours are in reverse order.
const unsigned red = (pxColor & 0xFF0000) >> 16;
const unsigned green = (pxColor & 0xFF00) >> 8;
const unsigned blue = pxColor & 0xFF;
//Combine the values in a more typical RGB format (as opposed to the bitmap way).
const int rgbValue = RGB(red, green, blue);
//Assign this RGB value to the pixel location in the vector o' vectors.
resultPixels[x][y] = rgbValue;
}
}
//Unlock the bits that we locked before.
bitmap.UnlockBits(bitmapData);
return resultPixels;
}
Here is how I would do it using GDIPlus Bitmap.LockBits method defined in the header GdiPlusBitmap.h:
Notice that since bitmaps are usually DWORD aligned you may want to discard this unused data that was needed for the alignment, as malat correctly commented..
Gdiplus::BitmapData bitmapData;
Gdiplus::Rect rect(0, 0, bitmap.GetWidth(), bitmap.GetHeight());
//get the bitmap data
if(Gdiplus::Ok == bitmap.LockBits(
&rect, //A rectangle structure that specifies the portion of the Bitmap to lock.
Gdiplus::ImageLockModeRead | Gdiplus::ImageLockModeWrite, //ImageLockMode values that specifies the access level (read/write) for the Bitmap.
bitmap.GetPixelFormat(),// PixelFormat values that specifies the data format of the Bitmap.
&bitmapData //BitmapData that will contain the information about the lock operation.
))
{
//get the lenght of the bitmap data in bytes
int len = bitmapData.Height * std::abs(bitmapData.Stride);
BYTE* buffer = new BYTE[len];
memcpy(bitmapData.Scan0, buffer, len);//copy it to an array of BYTEs
//...
//cleanup
bitmap.UnlockBits(&bitmapData);
delete []buffer;
}
Have you tried supplying the bytes when you create the bitmap:
int width = BMP_WIDTH;
int height = BMP_HEIGHT;
int stride = 4 * width;
BYTE bytes[stride * height];
Gdiplus::Bitmap cBitmap(width, height, stride, PixelFormat32bppRGB, bytes);
I'm using the glgrab code to try and grab a full-screen screenshot of the Mac screen. However, I want the bitmap data to be in the GL_RGB format. That is, each pixel should be in the format:
0x00RRGGBB
The original code specified the GL_BGRA format. However, changing that to GL_RGB gives me a completely blank result. The total source code I'm using is:
CGImageRef grabViaOpenGL(CGDirectDisplayID display, CGRect srcRect)
{
CGContextRef bitmap;
CGImageRef image;
void * data;
long bytewidth;
GLint width, height;
long bytes;
CGColorSpaceRef cSpace = CGColorSpaceCreateWithName (kCGColorSpaceGenericRGB);
CGLContextObj glContextObj;
CGLPixelFormatObj pixelFormatObj ;
GLint numPixelFormats ;
//CGLPixelFormatAttribute
int attribs[] =
{
// kCGLPFAClosestPolicy,
kCGLPFAFullScreen,
kCGLPFADisplayMask,
NULL, /* Display mask bit goes here */
kCGLPFAColorSize, 24,
kCGLPFAAlphaSize, 0,
kCGLPFADepthSize, 32,
kCGLPFASupersample,
NULL
} ;
if ( display == kCGNullDirectDisplay )
display = CGMainDisplayID();
attribs[2] = CGDisplayIDToOpenGLDisplayMask(display);
/* Build a full-screen GL context */
CGLChoosePixelFormat( (CGLPixelFormatAttribute*) attribs, &pixelFormatObj, &numPixelFormats );
if ( pixelFormatObj == NULL ) // No full screen context support
{
// GL didn't find any suitable pixel formats. Try again without the supersample bit:
attribs[10] = NULL;
CGLChoosePixelFormat( (CGLPixelFormatAttribute*) attribs, &pixelFormatObj, &numPixelFormats );
if (pixelFormatObj == NULL)
{
qDebug("Unable to find an openGL pixel format that meets constraints");
return NULL;
}
}
CGLCreateContext( pixelFormatObj, NULL, &glContextObj ) ;
CGLDestroyPixelFormat( pixelFormatObj ) ;
if ( glContextObj == NULL )
{
qDebug("Unable to create OpenGL context");
return NULL;
}
CGLSetCurrentContext( glContextObj ) ;
CGLSetFullScreen( glContextObj ) ;
glReadBuffer(GL_FRONT);
width = srcRect.size.width;
height = srcRect.size.height;
bytewidth = width * 4; // Assume 4 bytes/pixel for now
bytewidth = (bytewidth + 3) & ~3; // Align to 4 bytes
bytes = bytewidth * height; // width * height
/* Build bitmap context */
data = malloc(height * bytewidth);
if ( data == NULL )
{
CGLSetCurrentContext( NULL );
CGLClearDrawable( glContextObj ); // disassociate from full screen
CGLDestroyContext( glContextObj ); // and destroy the context
qDebug("OpenGL drawable clear failed");
return NULL;
}
bitmap = CGBitmapContextCreate(data, width, height, 8, bytewidth,
cSpace, kCGImageAlphaNoneSkipFirst /* XRGB */);
CFRelease(cSpace);
/* Read framebuffer into our bitmap */
glFinish(); /* Finish all OpenGL commands */
glPixelStorei(GL_PACK_ALIGNMENT, 4); /* Force 4-byte alignment */
glPixelStorei(GL_PACK_ROW_LENGTH, 0);
glPixelStorei(GL_PACK_SKIP_ROWS, 0);
glPixelStorei(GL_PACK_SKIP_PIXELS, 0);
/*
* Fetch the data in XRGB format, matching the bitmap context.
*/
glReadPixels((GLint)srcRect.origin.x, (GLint)srcRect.origin.y, width, height,
GL_RGB,
#ifdef __BIG_ENDIAN__
GL_UNSIGNED_INT_8_8_8_8_REV, // for PPC
#else
GL_UNSIGNED_INT_8_8_8_8, // for Intel! http://lists.apple.com/archives/quartz-dev/2006/May/msg00100.html
#endif
data);
/*
* glReadPixels generates a quadrant I raster, with origin in the lower left
* This isn't a problem for signal processing routines such as compressors,
* as they can simply use a negative 'advance' to move between scanlines.
* CGImageRef and CGBitmapContext assume a quadrant III raster, though, so we need to
* invert it. Pixel reformatting can also be done here.
*/
swizzleBitmap(data, bytewidth, height);
/* Make an image out of our bitmap; does a cheap vm_copy of the bitmap */
image = CGBitmapContextCreateImage(bitmap);
/* Get rid of bitmap */
CFRelease(bitmap);
free(data);
/* Get rid of GL context */
CGLSetCurrentContext( NULL );
CGLClearDrawable( glContextObj ); // disassociate from full screen
CGLDestroyContext( glContextObj ); // and destroy the context
/* Returned image has a reference count of 1 */
return image;
}
I'm completely new to OpenGL, so I'd appreciate some pointers in the right direction. Cheers!
Update:
After some experimentation, I have managed to narrow my problem down. My problem is that while I don't want the alpha component, I Do want each pixel to be packed to 4-byte boundaries. Now, when I specify GL_RGB or GL_BGR formats to the glReadPixels call, I get the bitmap data packed in 3 byte blocks. When I specify GL_RGBA, or GL_BGRA, I get four byte blocks, but always with the alpha channel component last.
I then tried changing the value passed to
bitmap = CGBitmapContextCreate(data, width, height, 8, bytewidth,cSpace, kCGImageAlphaNoneSkipFirst /* XRGB */);
however, no variations of AlphaNoneSkipFirst or AlphaNoneSkipLast puts the alpha channel at the start of the pixel byte block.
Any ideas?
I'm not a Mac guy, but if you can get RGBA data and want XRGB, can't you just bitshift each pixel down eight bits?
foreach( unsigned int* RGBA_pixel, pixbuf )
{
(*RGBA_pixel) = (*RGBA_pixel) >> 8;
}
Try with GL_UNSIGNED_BYTE instead of GL_UNSIGNED_INT_8_8_8_8_REV / GL_UNSIGNED_INT_8_8_8_8.
Although it seems you want GL_RGBA instead -- then it should work with either 8_8_8_8_REV or 8_8_8_8 instead.
When I use GL_BGRA the data is returned pre-swizzled which is confirmed because the colors look correct when i display the result in a window.
Contact me if you want the project I created. Hope this helps.