fix sprites for pixel ratios that are not 1 and 2

- OpenGL ES 2 doesn't allow NPOT textures with wrap-around
- The Sprite object reported the map's pixelRatio, even though it loaded @2x assets
- Copying icons from the sprite into the atlas now uses bilinear scaling to scale up to the actual size

6 files changed, 73 insertions, 0 deletions

diff --git a/test/fixtures/sprites/atlas_reference.bin b/test/fixtures/sprites/atlas_reference.bin
new file mode 100644
index 0000000000..57eb28bd93
--- /dev/null
+++ b/test/fixtures/sprites/atlas_reference.bin
diff --git a/test/fixtures/sprites/atlas_reference.png b/test/fixtures/sprites/atlas_reference.png
new file mode 100644
index 0000000000..86fad30983
--- /dev/null
+++ b/test/fixtures/sprites/atlas_reference.png
diff --git a/test/fixtures/sprites/bright.bin b/test/fixtures/sprites/bright.bin
new file mode 100644
index 0000000000..3aee130074
--- /dev/null
+++ b/test/fixtures/sprites/bright.bin
diff --git a/test/fixtures/sprites/convert_sprite.js b/test/fixtures/sprites/convert_sprite.js
new file mode 100644
index 0000000000..ba4ff5c29f
--- /dev/null
+++ b/test/fixtures/sprites/convert_sprite.js
@@ -0,0 +1,19 @@
+// Converts a PNG image to a custom "image format" that has a uint32_t width/height prefix and then
+// raw RGBA data. We can't use the built-in PNG reading routines because they are reading
+// premultiplied images by default.
+
+var fs = require('fs');
+var zlib = require('zlib');
+var PNG = require('png-js');
+var png = PNG.load('styles/sprites/bright.png');
+png.decodePixels(function(data) {
+    var result = new Buffer(8 + data.length);
+    result.writeUInt32BE(png.width, 0);
+    result.writeUInt32BE(png.height, 4);
+    data.copy(result, 8);
+
+    zlib.deflate(result, function(err, data) {
+        if (err) throw err;
+        fs.writeFileSync('test/fixtures/sprites/bright.bin', data);
+    });
+});
diff --git a/test/miscellaneous/bilinear.cpp b/test/miscellaneous/bilinear.cpp
new file mode 100644
index 0000000000..b7730303a0
--- /dev/null
+++ b/test/miscellaneous/bilinear.cpp
@@ -0,0 +1,53 @@
+#include "../fixtures/util.hpp"
+#include <mbgl/util/compression.hpp>
+#include <mbgl/util/scaling.hpp>
+#include <mbgl/util/image.hpp>
+#include <mbgl/util/io.hpp>
+#include <mbgl/util/std.hpp>
+
+#include <algorithm>
+#include <cstring>
+
+using namespace mbgl;
+
+TEST(Bilinear, Scaling) {
+    // We're reading from a custom "image format" that has a uint32_t width/height prefix and then
+    // raw RGBA data. We can't use the built-in PNG reading routines because they are reading
+    // premultiplied images by default.
+    const std::string sprite = util::decompress(util::read_file("test/fixtures/sprites/bright.bin"));
+    const uint8_t *src = reinterpret_cast<const uint8_t *>(sprite.data());
+    ASSERT_GT(sprite.length(), 8u);
+    const uint32_t width = src[0] << 24 | src[1] << 16 | src[2] << 8 | src[3];
+    const uint32_t height = src[4] << 24 | src[5] << 16 | src[6] << 8 | src[7];
+    ASSERT_EQ(sprite.length(), 2 * sizeof(uint32_t) + width * height * sizeof(uint32_t));
+
+    const uint32_t *srcData = reinterpret_cast<const uint32_t *>(src + 8);
+    const vec2<uint32_t> srcSize { width, height };
+    const vec2<uint32_t> dstSize { 128, 128 };
+    auto dst = util::make_unique<uint32_t[]>(dstSize.x * dstSize.y);
+    uint32_t *dstData = dst.get();
+    std::fill(dstData, dstData + dstSize.x * dstSize.y, 0xFFFF00FF);
+
+    util::bilinearScale(srcData, srcSize, { 0, 0, 24, 24 }, dstData, dstSize, { 8, 8, 24, 24 });
+    util::bilinearScale(srcData, srcSize, { 26, 0, 24, 24 }, dstData, dstSize, { 0, 40, 48, 48 });
+    util::bilinearScale(srcData, srcSize, { 26, 26, 24, 24 }, dstData, dstSize, { 52, 40, 36, 36 });
+    util::bilinearScale(srcData, srcSize, { 26, 26, 24, 24 }, dstData, dstSize, { 52, 40, 36, 36 });
+    util::bilinearScale(srcData, srcSize, { 104, 0, 24, 24 }, dstData, dstSize, { 96, 0, 48, 48 });
+    util::bilinearScale(srcData, srcSize, { 52, 260, 24, 24 }, dstData, dstSize, { 108, 108, 38, 38 });
+    util::bilinearScale(srcData, srcSize, { 380, 0, 24, 24 }, dstData, dstSize, { 36, 0, 24, 24 });
+    util::bilinearScale(srcData, srcSize, { 396, 396, 24, 24 }, dstData, dstSize, { 0, 0, 50, 50 });
+    util::bilinearScale(srcData, srcSize, { 380, 182, 12, 12 }, dstData, dstSize, { 52, 80, 24, 24 });
+
+    // From the bottom
+    util::bilinearScale(srcData, srcSize, { 252, 380, 12, 12 }, dstData, dstSize, { 0, 90, 12, 12 });
+    util::bilinearScale(srcData, srcSize, { 252, 380, 12, 12 }, dstData, dstSize, { 18, 90, 24, 24 });
+
+    const std::string data { reinterpret_cast<char *>(dstData), dstSize.x * dstSize.y * sizeof(uint32_t) };
+    util::write_file("test/fixtures/sprites/atlas_actual.png", util::compress_png(dstSize.x, dstSize.y, dstData));
+    util::write_file("test/fixtures/sprites/atlas_actual.bin", util::compress(data));
+
+    const std::string reference = util::decompress(util::read_file("test/fixtures/sprites/atlas_reference.bin"));
+
+    EXPECT_EQ(reference.size(), data.size());
+    EXPECT_TRUE(0 == std::memcmp(data.data(), reference.data(), data.size()));
+}
diff --git a/test/test.gyp b/test/test.gyp
index 719207a02e..c333a40064 100644
--- a/test/test.gyp
+++ b/test/test.gyp
@@ -38,6 +38,7 @@
         'headless/headless.cpp',
 
         'miscellaneous/clip_ids.cpp',
+        'miscellaneous/bilinear.cpp',
         'miscellaneous/comparisons.cpp',
         'miscellaneous/enums.cpp',
         'miscellaneous/functions.cpp',