Restore screenshot functionality and Targa saving

With the migration to OpenGL ES2 from OpenGL 1.1 some parameters of
`glReadPixels` became more restrictive, only allowing two distinct pairs
of format/type; neither of which matched the format we needed to capture
screenshots.

This change reads out pixels in an always-supported format (RGBA) and
converts it to the desired RGB as it flips the image. Stubbed out
functionality to write Targa files was also reimplemented via stb_image.

Author: zao

engine/core/core_image.cpp

@@ -50,7 +50,7 @@ image_c::~image_c()
 
 void image_c::CopyRaw(int inType, dword inWidth, dword inHeight, const byte* inDat)
 {
-	if (dat) delete dat;
+	if (dat) delete[] dat;
 	comp = inType & 0xF;
 	type = inType;
 	width = inWidth;
@@ -61,7 +61,7 @@ void image_c::CopyRaw(int inType, dword inWidth, dword inHeight, const byte* inD
 
 void image_c::Free()
 {
-	delete dat;
+	delete[] dat;
 	dat = NULL;
 }
 
@@ -188,7 +188,7 @@ bool targa_c::Load(const char* fileName)
 				int rlen = ((rlehdr & 0x7F) + 1) * comp; 
 				if (x + rlen > rowSize) {
 					con->Warning("TGA '%s': invalid RLE coding (overlong row)", fileName);
-					delete dat;
+					delete[] dat;
 					return true;
 				}
 				if (rlehdr & 0x80) {
@@ -225,7 +225,22 @@ bool targa_c::Load(const char* fileName)
 
 bool targa_c::Save(const char* fileName)
 {
-	return true;
+	if (type != IMGTYPE_RGB && type != IMGTYPE_RGBA) {
+		return true;
+	}
+
+	// Open file
+	fileOutputStream_c out;
+	if (out.FileOpen(fileName, true)) {
+		return true;
+	}
+
+	auto rc = stbi_write_tga_to_func([](void* ctx, void* data, int size) {
+		auto out = (fileOutputStream_c*)ctx;
+		out->Write(data, size);
+		}, &out, width, height, comp, dat);
+
+	return !rc;
 }
 
 bool targa_c::ImageInfo(const char* fileName, imageInfo_s* info)
@@ -277,14 +292,14 @@ bool jpeg_c::Load(const char* fileName)
 		return true;
 	}
 	int x, y, in_comp;
-	if (!stbi_info_from_memory(fileData.data(), fileData.size(), &x, &y, &in_comp)) {
+	if (!stbi_info_from_memory(fileData.data(), (int)fileData.size(), &x, &y, &in_comp)) {
 		return true;
 	}
 	if (in_comp != 1 && in_comp != 3) {
 		con->Warning("JPEG '%s': unsupported component count '%d'", fileName, comp);
 		return true;
 	}
-	stbi_uc* data = stbi_load_from_memory(fileData.data(), fileData.size(), &x, &y, &in_comp, in_comp);
+	stbi_uc* data = stbi_load_from_memory(fileData.data(), (int)fileData.size(), &x, &y, &in_comp, in_comp);
 	if (!data) {
 		stbi_image_free(data);
 		return true;
@@ -335,7 +350,7 @@ bool jpeg_c::ImageInfo(const char* fileName, imageInfo_s* info)
 		return true;
 	}
 	int x, y, comp;
-	if (stbi_info_from_memory(fileData.data(), fileData.size(), &x, &y, &comp)) {
+	if (stbi_info_from_memory(fileData.data(), (int)fileData.size(), &x, &y, &comp)) {
 		return true;
 	}
 
@@ -366,14 +381,14 @@ bool png_c::Load(const char* fileName)
 		return true;
 	}
 	int x, y, in_comp;
-	if (!stbi_info_from_memory(fileData.data(), fileData.size(), &x, &y, &in_comp)) {
+	if (!stbi_info_from_memory(fileData.data(), (int)fileData.size(), &x, &y, &in_comp)) {
 		return true;
 	}
 	width = x;
 	height = y;
 	comp = (in_comp == 1 || in_comp == 3) ? 3 : 4;
 	type = comp == 3 ? IMGTYPE_RGB : IMGTYPE_RGBA;
-	stbi_uc* data = stbi_load_from_memory(fileData.data(), fileData.size(), &x, &y, &in_comp, comp);
+	stbi_uc* data = stbi_load_from_memory(fileData.data(), (int)fileData.size(), &x, &y, &in_comp, comp);
 	if (!data) {
 		stbi_image_free(data);
 		return true;
@@ -420,7 +435,7 @@ bool png_c::ImageInfo(const char* fileName, imageInfo_s* info)
 		return true;
 	}
 	int x, y, comp;
-	if (stbi_info_from_memory(fileData.data(), fileData.size(), &x, &y, &comp)) {
+	if (stbi_info_from_memory(fileData.data(), (int)fileData.size(), &x, &y, &comp)) {
 		return true;
 	}
 
@@ -449,7 +464,7 @@ bool gif_c::Load(const char* fileName)
 			return true;
 		}
 		int x, y, in_comp;
-		stbi_uc* data = stbi_load_from_memory(fileData.data(), fileData.size(), &x, &y, &in_comp, 4);
+		stbi_uc* data = stbi_load_from_memory(fileData.data(), (int)fileData.size(), &x, &y, &in_comp, 4);
 		if (!data || in_comp != 4) {
 			stbi_image_free(data);
 			return true;

engine/render/r_main.cpp

@@ -1830,25 +1830,45 @@ void r_renderer_c::C_Screenshot(IConsole* conHnd, args_c& args)
 
 void r_renderer_c::DoScreenshot(image_c* i, const char* ext)
 {
-	int xs = sys->video->vid.size[0];
-	int ys = sys->video->vid.size[1];
+	if (i->type != IMGTYPE_RGB) {
+		return;
+	}
+	auto& rt = rttMain[presentRtt];
+	int const xs = rt.width;
+	int const ys = rt.height;
 
-	int size = xs * ys * 3;
-	byte* sbuf = new byte[size];
+	// Pixel reading only supports RGBA and an implementation-specific format.
+	// Use RGBA for convenience as that's close enough to what we want to save in the end.
+	int const readSize = xs * ys * 4;
+	int const writeSize = xs * ys * 3;
+	std::vector<byte> sbuf(readSize);
 
 	// Read the front buffer
+	GLint oldFb{};
+	GLenum oglErr = glGetError();
+	GLenum implColorReadFormat{}, implColorReadType{};
+	glGetIntegerv(GL_FRAMEBUFFER_BINDING, &oldFb);
+	glBindFramebuffer(GL_FRAMEBUFFER, rttMain[presentRtt].framebuffer);
 	glPixelStorei(GL_PACK_ALIGNMENT, 1);
-	glReadPixels(0, 0, xs, ys, r_tex_c::GLTypeForImgType(i->type), GL_UNSIGNED_BYTE, sbuf);
-
-	// Flip the image
-	int	span = xs * 3;
-	byte* ss = new byte[size];
-	byte* p1 = sbuf;
-	byte* p2 = ss + size - span;
-	for (int y = 0; y < ys; y++, p1 += span, p2 -= span) {
-		memcpy(p2, p1, span);
+	glReadPixels(0, 0, xs, ys, GL_RGBA, GL_UNSIGNED_BYTE, sbuf.data());
+	oglErr = glGetError();
+	glBindFramebuffer(GL_FRAMEBUFFER, oldFb);
+
+	// Flip and convert the image to RGB
+	int const readSpan = xs * 4;
+	int	const writeSpan = xs * 3;
+	byte* ss = new byte[writeSize]; // This is a raw pointer as ownership is taken by the image object.
+	byte* p1 = sbuf.data();
+	byte* p2 = ss + writeSize - writeSpan;
+	for (int y = 0; y < ys; ++y, p2 -= writeSpan * 2) {
+		for (int x = 0; x < xs; ++x) {
+			*p2++ = *p1++; // R
+			*p2++ = *p1++; // G
+			*p2++ = *p1++; // B
+			p1++; // A
+		}
 	}
-	delete[] sbuf;
+	sbuf.clear();
 
 	// Set image info
 	i->dat = ss;