TgaImporter: ported to work also with OpenGL ES.

OpenGL ES doesn't have BGR and BGRA, swizzling pixel values to make it
RGB and RGBA there.

src/Plugins/TgaImporter/Test/TgaImporterTest.cpp

@@ -95,15 +95,26 @@ void TgaImporterTest::bits24() {
         0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 3, 0, 24, 0,
         1, 2, 3, 2, 3, 4, 3, 4, 5, 4, 5, 6, 5, 6, 7, 6, 7, 8
     };
+    #ifndef MAGNUM_TARGET_GLES
+    const char* pixels = data + 18;
+    #else
+    const char pixels[] = {
+        3, 2, 1, 4, 3, 2, 5, 4, 3, 6, 5, 4, 7, 6, 5, 8, 7, 6
+    };
+    #endif
     std::istringstream in(string(data, sizeof(data)));
 
     TgaImporter importer;
     CORRADE_VERIFY(importer.open(in));
     auto image = importer.image2D(0);
+    #ifndef MAGNUM_TARGET_GLES
     CORRADE_VERIFY(image->components() == AbstractImage::Components::BGR);
+    #else
+    CORRADE_VERIFY(image->components() == AbstractImage::Components::RGB);
+    #endif
     CORRADE_COMPARE(image->dimensions(), Math::Vector2<GLsizei>(2, 3));
     CORRADE_VERIFY(image->type() == TypeTraits<GLubyte>::imageType());
-    CORRADE_COMPARE(string(static_cast<const char*>(image->data()), 2*3*3), string(data + 18, 2*3*3));
+    CORRADE_COMPARE(string(static_cast<const char*>(image->data()), 2*3*3), string(pixels, 2*3*3));
 }
 
 void TgaImporterTest::bits32() {
@@ -111,15 +122,26 @@ void TgaImporterTest::bits32() {
         0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 3, 0, 32, 0,
         1, 2, 3, 1, 2, 3, 4, 1, 3, 4, 5, 1, 4, 5, 6, 1, 5, 6, 7, 1, 6, 7, 8, 1
     };
+    #ifndef MAGNUM_TARGET_GLES
+    const char* pixels = data + 18;
+    #else
+    const char pixels[] = {
+        3, 2, 1, 1, 4, 3, 2, 1, 5, 4, 3, 1, 6, 5, 4, 1, 7, 6, 5, 1, 8, 7, 6, 1
+    };
+    #endif
     std::istringstream in(string(data, sizeof(data)));
 
     TgaImporter importer;
     CORRADE_VERIFY(importer.open(in));
     auto image = importer.image2D(0);
+    #ifndef MAGNUM_TARGET_GLES
     CORRADE_VERIFY(image->components() == AbstractImage::Components::BGRA);
+    #else
+    CORRADE_VERIFY(image->components() == AbstractImage::Components::RGBA);
+    #endif
     CORRADE_COMPARE(image->dimensions(), Math::Vector2<GLsizei>(2, 3));
     CORRADE_VERIFY(image->type() == TypeTraits<GLubyte>::imageType());
-    CORRADE_COMPARE(string(static_cast<const char*>(image->data()), 2*3*3), string(data + 18, 2*3*3));
+    CORRADE_COMPARE(string(static_cast<const char*>(image->data()), 2*3*3), string(pixels, 2*3*3));
 }
 
 }}}}

src/Plugins/TgaImporter/TgaImporter.cpp

@@ -15,9 +15,11 @@
 
 #include "TgaImporter.h"
 
+#include <algorithm>
 #include <Utility/Endianness.h>
 
 #include "Math/Vector2.h"
+#include "Math/Swizzle.h"
 #include "Trade/ImageData.h"
 
 using namespace std;
@@ -76,10 +78,18 @@ bool TgaImporter::open(istream& in, const string& name) {
     AbstractImage::Components components;
     switch(header.bpp) {
         case 24:
+            #ifndef MAGNUM_TARGET_GLES
             components = AbstractImage::Components::BGR;
+            #else
+            components = AbstractImage::Components::RGB;
+            #endif
             break;
         case 32:
+            #ifndef MAGNUM_TARGET_GLES
             components = AbstractImage::Components::BGRA;
+            #else
+            components = AbstractImage::Components::RGBA;
+            #endif
             break;
         default:
             Error() << "TgaImporter: unsupported bits-per-pixel:" << int(header.bpp);
@@ -92,6 +102,18 @@ bool TgaImporter::open(istream& in, const string& name) {
 
     Math::Vector2<GLsizei> dimensions(header.width, header.height);
 
+    #ifdef MAGNUM_TARGET_GLES
+    if(components == AbstractImage::Components::RGB) {
+        Math::Vector3<GLubyte>* data = reinterpret_cast<Math::Vector3<GLubyte>*>(buffer);
+        std::transform(data, data + dimensions.product(), data,
+            [](Math::Vector3<GLubyte> pixel) { return Math::swizzle<'b', 'g', 'r'>(pixel); });
+    } else /* RGBA */ {
+        Math::Vector4<GLubyte>* data = reinterpret_cast<Math::Vector4<GLubyte>*>(buffer);
+        std::transform(data, data + dimensions.product(), data,
+            [](Math::Vector4<GLubyte> pixel) { return Math::swizzle<'b', 'g', 'r', 'a'>(pixel); });
+    }
+    #endif
+
     _image = new ImageData2D(name, dimensions, components, buffer);
     return true;
 }