TextureTools: support padding in atlas().

src/TextureTools/Atlas.cpp

@@ -20,7 +20,7 @@
 
 namespace Magnum { namespace TextureTools {
 
-std::vector<Rectanglei> atlas(const Vector2i& atlasSize, const std::vector<Vector2i>& sizes) {
+std::vector<Rectanglei> atlas(const Vector2i& atlasSize, const std::vector<Vector2i>& sizes, const Vector2i& padding) {
     if(sizes.empty()) return {};
 
     /* Size of largest texture */
@@ -31,10 +31,11 @@ std::vector<Rectanglei> atlas(const Vector2i& atlasSize, const std::vector<Vecto
     std::vector<Rectanglei> atlas;
 
     /* Columns and rows */
-    const Vector2i gridSize = atlasSize/maxSize;
+    const Vector2i paddedSize = maxSize+2*padding;
+    const Vector2i gridSize = atlasSize/paddedSize;
     if(std::size_t(gridSize.product()) < sizes.size()) {
         Error() << "TextureTools::atlas(): requested atlas size" << atlasSize
-                << "is too small to fit" << sizes.size() << maxSize
+                << "is too small to fit" << sizes.size() << paddedSize
                 << "textures. Generated atlas will be empty.";
         return atlas;
     }
@@ -43,7 +44,7 @@ std::vector<Rectanglei> atlas(const Vector2i& atlasSize, const std::vector<Vecto
 
     atlas.reserve(sizes.size());
     for(std::size_t i = 0; i != sizes.size(); ++i)
-        atlas.push_back(Rectanglei::fromSize(Vector2i(i%gridSize.x(), i/gridSize.x())*maxSize, sizes[i]));
+        atlas.push_back(Rectanglei::fromSize(Vector2i(i%gridSize.x(), i/gridSize.x())*paddedSize+padding, sizes[i]));
 
     return atlas;
 }

src/TextureTools/Atlas.h

@@ -21,6 +21,7 @@
 
 #include <vector>
 
+#include "Math/Vector2.h"
 #include "Magnum.h"
 
 #include "magnumTextureToolsVisibility.h"
@@ -31,11 +32,16 @@ namespace Magnum { namespace TextureTools {
 @brief Pack textures into texture atlas
 @param atlasSize    Size of resulting atlas
 @param sizes        Sizes of all textures in the atlas
+@param padding      Padding around each texture
 
 Packs many small textures into one larger. If the textures cannot be packed
 into required size, empty vector is returned.
+
+Padding is added twice to each size and the atlas is laid out so the padding
+don't overlap. Returned sizes are the same as original sizes, i.e. without the
+padding.
 */
-std::vector<Rectanglei> MAGNUM_TEXTURETOOLS_EXPORT atlas(const Vector2i& atlasSize, const std::vector<Vector2i>& sizes);
+std::vector<Rectanglei> MAGNUM_TEXTURETOOLS_EXPORT atlas(const Vector2i& atlasSize, const std::vector<Vector2i>& sizes, const Vector2i& padding = Vector2i());
 
 }}
 

src/TextureTools/Test/AtlasTest.cpp

@@ -26,12 +26,14 @@ class AtlasTest: public Corrade::TestSuite::Tester {
         explicit AtlasTest();
 
         void create();
+        void createPadding();
         void createEmpty();
         void createTooSmall();
 };
 
 AtlasTest::AtlasTest() {
     addTests(&AtlasTest::create,
+             &AtlasTest::createPadding,
              &AtlasTest::createEmpty,
              &AtlasTest::createTooSmall);
 }
@@ -50,6 +52,20 @@ void AtlasTest::create() {
         Rectanglei::fromSize({0, 25}, {23, 25})}));
 }
 
+void AtlasTest::createPadding() {
+    std::vector<Rectanglei> atlas = TextureTools::atlas({64, 64}, {
+        {8, 16},
+        {28, 13},
+        {19, 23}
+    }, {2, 1});
+
+    CORRADE_COMPARE(atlas.size(), 3);
+    CORRADE_COMPARE(atlas, (std::vector<Rectanglei>{
+        Rectanglei::fromSize({2, 1}, {8, 16}),
+        Rectanglei::fromSize({34, 1}, {28, 13}),
+        Rectanglei::fromSize({2, 26}, {19, 23})}));
+}
+
 void AtlasTest::createEmpty() {
     std::vector<Rectanglei> atlas = TextureTools::atlas({}, {});
     CORRADE_VERIFY(atlas.empty());
@@ -60,10 +76,10 @@ void AtlasTest::createTooSmall() {
     Error::setOutput(&o);
 
     std::vector<Rectanglei> atlas = TextureTools::atlas({64, 32}, {
-        {12, 18},
-        {25, 15},
-        {23, 31}
-    });
+        {8, 16},
+        {21, 13},
+        {19, 29}
+    }, {2, 1});
     CORRADE_VERIFY(atlas.empty());
     CORRADE_COMPARE(o.str(), "TextureTools::atlas(): requested atlas size Vector(64, 32) is too small to fit 3 Vector(25, 31) textures. Generated atlas will be empty.\n");
 }