diff --git a/include/mbgl/map/still_image.hpp b/include/mbgl/map/still_image.hpp
index b9ce0620f..36922fe95 100644
--- a/include/mbgl/map/still_image.hpp
+++ b/include/mbgl/map/still_image.hpp
@@ -3,17 +3,15 @@
 
 #include <mbgl/util/noncopyable.hpp>
 
-#include <string>
 #include <cstdint>
 
 namespace mbgl {
 
 class StillImage : util::noncopyable {
 public:
-    uint16_t width = 0;
-    uint16_t height = 0;
-    using Pixel = uint32_t;
-    std::unique_ptr<Pixel[]> pixels;
+    size_t width = 0;
+    size_t height = 0;
+    std::unique_ptr<uint8_t[]> pixels;
 };
 
 }
diff --git a/include/mbgl/platform/default/image_reader.hpp b/include/mbgl/platform/default/image_reader.hpp
index 52a67a283..8e293d8be 100644
--- a/include/mbgl/platform/default/image_reader.hpp
+++ b/include/mbgl/platform/default/image_reader.hpp
@@ -31,11 +31,11 @@ struct ImageReader : private noncopyable
     virtual unsigned height() const=0;
     virtual bool hasAlpha() const=0;
     virtual bool premultipliedAlpha() const=0;
-    virtual void read(unsigned x,unsigned y, unsigned width, unsigned height, char* image)=0;
+    virtual void read(unsigned x, unsigned y, unsigned width, unsigned height, uint8_t* image)=0;
     virtual ~ImageReader() {}
 };
 
-std::unique_ptr<ImageReader> getImageReader(char const* data, size_t size);
+std::unique_ptr<ImageReader> getImageReader(const uint8_t* data, size_t size);
 
 }}
 
diff --git a/include/mbgl/platform/default/jpeg_reader.hpp b/include/mbgl/platform/default/jpeg_reader.hpp
index 3e64ce291..d87700535 100644
--- a/include/mbgl/platform/default/jpeg_reader.hpp
+++ b/include/mbgl/platform/default/jpeg_reader.hpp
@@ -51,13 +51,13 @@ private:
     unsigned width_;
     unsigned height_;
 public:
-    JpegReader(char const* data, size_t size);
+    JpegReader(const uint8_t* data, size_t size);
     ~JpegReader();
     unsigned width() const;
     unsigned height() const;
     inline bool hasAlpha() const { return false; }
     inline bool premultipliedAlpha() const { return true; }
-    void read(unsigned x,unsigned y, unsigned w, unsigned h, char *image);
+    void read(unsigned x, unsigned y, unsigned w, unsigned h, uint8_t* image);
 private:
     void init();
     static void on_error(j_common_ptr cinfo);
diff --git a/include/mbgl/platform/default/png_reader.hpp b/include/mbgl/platform/default/png_reader.hpp
index 5cbbc51e7..9d6af91da 100644
--- a/include/mbgl/platform/default/png_reader.hpp
+++ b/include/mbgl/platform/default/png_reader.hpp
@@ -49,13 +49,13 @@ private:
     int color_type_;
     bool has_alpha_;
 public:
-    PngReader(char const* data, std::size_t size);
+    PngReader(const uint8_t* data, std::size_t size);
     ~PngReader();
     unsigned width() const;
     unsigned height() const;
     inline bool hasAlpha() const { return has_alpha_; }
     bool premultipliedAlpha() const { return true; } // png_set_alpha_mode(png, PNG_ALPHA_PREMULTIPLIED, 2.2)
-    void read(unsigned x,unsigned y, unsigned width, unsigned height, char * image);
+    void read(unsigned x,unsigned y, unsigned width, unsigned height, uint8_t* image);
 private:
     void init();
     static void png_read_data(png_structp png_ptr, png_bytep data, png_size_t length);
diff --git a/include/mbgl/util/image.hpp b/include/mbgl/util/image.hpp
index f58c2c098..fc4078501 100644
--- a/include/mbgl/util/image.hpp
+++ b/include/mbgl/util/image.hpp
@@ -7,14 +7,14 @@
 namespace mbgl {
 namespace util {
 
-std::string compress_png(int width, int height, const void *rgba);
+std::string compress_png(size_t width, size_t height, const uint8_t* rgba);
 
 
 class Image {
 public:
-    explicit Image(const std::string &img);
+    explicit Image(const std::string& img);
 
-    inline const char *getData() const { return img.get(); }
+    inline const uint8_t* getData() const { return img.get(); }
     inline uint32_t getWidth() const { return width; }
     inline uint32_t getHeight() const { return height; }
     inline operator bool() const { return img && width && height; }
@@ -24,7 +24,7 @@ private:
     uint32_t width = 0, height = 0;
 
     // the raw image data
-    std::unique_ptr<char[]> img;
+    std::unique_ptr<uint8_t[]> img;
 };
 
 
diff --git a/platform/darwin/image.mm b/platform/darwin/image.mm
index 31373e9d1..8965f1ea9 100644
--- a/platform/darwin/image.mm
+++ b/platform/darwin/image.mm
@@ -11,7 +11,7 @@
 namespace mbgl {
 namespace util {
 
-std::string compress_png(int width, int height, const void *rgba) {
+std::string compress_png(size_t width, size_t height, const uint8_t* rgba) {
     CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, rgba, width * height * 4, NULL);
     if (!provider) {
         return "";
@@ -97,7 +97,7 @@ Image::Image(const std::string &source_data) {
     height = uint32_t(CGImageGetHeight(image));
     CGRect rect = {{ 0, 0 }, { static_cast<CGFloat>(width), static_cast<CGFloat>(height) }};
 
-    img = std::make_unique<char[]>(width * height * 4);
+    img = std::make_unique<uint8_t[]>(width * height * 4);
     CGContextRef context = CGBitmapContextCreate(img.get(), width, height, 8, width * 4,
         color_space, kCGImageAlphaPremultipliedLast);
     if (!context) {
diff --git a/platform/default/headless_view.cpp b/platform/default/headless_view.cpp
index 0587f5f38..fa83f6596 100644
--- a/platform/default/headless_view.cpp
+++ b/platform/default/headless_view.cpp
@@ -179,7 +179,7 @@ std::unique_ptr<StillImage> HeadlessView::readStillImage() {
     auto image = std::make_unique<StillImage>();
     image->width = w;
     image->height = h;
-    image->pixels = std::make_unique<uint32_t[]>(w * h);
+    image->pixels = std::make_unique<uint8_t[]>(w * h * 4);
 
     MBGL_CHECK_ERROR(glReadPixels(0, 0, w, h, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels.get()));
 
diff --git a/platform/default/image.cpp b/platform/default/image.cpp
index 1562a06b7..bbd5d02b6 100644
--- a/platform/default/image.cpp
+++ b/platform/default/image.cpp
@@ -27,7 +27,7 @@ const static bool png_version_check = []() {
 namespace mbgl {
 namespace util {
 
-std::string compress_png(int width, int height, const void *rgba) {
+std::string compress_png(size_t width, size_t height, const uint8_t* rgba) {
     png_voidp error_ptr = 0;
     png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, error_ptr, NULL, NULL);
     if (!png_ptr) {
@@ -63,7 +63,7 @@ std::string compress_png(int width, int height, const void *rgba) {
         png_bytep *rows = nullptr;
     } pointers(height);
 
-    for (int i = 0; i < height; i++) {
+    for (size_t i = 0; i < height; i++) {
         pointers.rows[i] = (png_bytep)((png_bytep)rgba + width * 4 * i);
     }
 
@@ -78,10 +78,10 @@ Image::Image(std::string const& data)
 {
     try
     {
-        auto reader = getImageReader(data.c_str(), data.size());
+        auto reader = getImageReader(reinterpret_cast<const uint8_t*>(data.c_str()), data.size());
         width = reader->width();
         height = reader->height();
-        img = std::make_unique<char[]>(width * height * 4);
+        img = std::make_unique<uint8_t[]>(width * height * 4);
         reader->read(0, 0, width, height, img.get());
     }
     catch (ImageReaderException const& ex)
diff --git a/platform/default/image_reader.cpp b/platform/default/image_reader.cpp
index e80ccb681..3d27db58c 100644
--- a/platform/default/image_reader.cpp
+++ b/platform/default/image_reader.cpp
@@ -7,7 +7,7 @@
 
 namespace mbgl { namespace util {
 
-inline boost::optional<std::string> type_from_bytes(char const* data, size_t size)
+inline boost::optional<std::string> type_from_bytes(const uint8_t* data, size_t size)
 {
     using result_type = boost::optional<std::string>;
     if (size >= 4)
@@ -42,9 +42,9 @@ inline boost::optional<std::string> type_from_bytes(char const* data, size_t siz
     return result_type();
 }
 
-std::unique_ptr<ImageReader> getImageReader(char const* data, size_t size)
+std::unique_ptr<ImageReader> getImageReader(const uint8_t* data, size_t size)
 {
-    boost::optional<std::string> type = type_from_bytes(data,size);
+    boost::optional<std::string> type = type_from_bytes(data, size);
     if (type)
     {
         if (*type == "png")
diff --git a/platform/default/jpeg_reader.cpp b/platform/default/jpeg_reader.cpp
index f89e76687..dac18f32d 100644
--- a/platform/default/jpeg_reader.cpp
+++ b/platform/default/jpeg_reader.cpp
@@ -13,8 +13,8 @@ namespace mbgl { namespace util {
 
 // ctor
 template <typename T>
-JpegReader<T>::JpegReader(char const* data, size_t size)
-    : source_(data, size),
+JpegReader<T>::JpegReader(const uint8_t* data, size_t size)
+    : source_(reinterpret_cast<const char*>(data), size),
       stream_(source_),
       width_(0),
       height_(0)
@@ -145,7 +145,7 @@ unsigned JpegReader<T>::height() const
 }
 
 template <typename T>
-void JpegReader<T>::read(unsigned x0, unsigned y0, unsigned w, unsigned h, char* image)
+void JpegReader<T>::read(unsigned x0, unsigned y0, unsigned w, unsigned h, uint8_t* image)
 {
     stream_.clear();
     stream_.seekg(0, std::ios_base::beg);
diff --git a/platform/default/png_reader.cpp b/platform/default/png_reader.cpp
index ede7e52be..204c4874f 100644
--- a/platform/default/png_reader.cpp
+++ b/platform/default/png_reader.cpp
@@ -40,8 +40,8 @@ void PngReader<T>::png_read_data(png_structp png_ptr, png_bytep data, png_size_t
 }
 
 template <typename T>
-PngReader<T>::PngReader(char const* data, std::size_t size)
-    : source_(data,size),
+PngReader<T>::PngReader(const uint8_t* data, std::size_t size)
+    : source_(reinterpret_cast<const char*>(data), size),
       stream_(source_),
       width_(0),
       height_(0),
@@ -115,7 +115,7 @@ unsigned PngReader<T>::height() const
 }
 
 template <typename T>
-void PngReader<T>::read(unsigned x0, unsigned y0, unsigned w, unsigned h, char * image)
+void PngReader<T>::read(unsigned x0, unsigned y0, unsigned w, unsigned h, uint8_t* image)
 {
     stream_.clear();
     stream_.seekg(0, std::ios_base::beg);
diff --git a/platform/node/src/node_map.cpp b/platform/node/src/node_map.cpp
index 99fbb919e..eb9220548 100644
--- a/platform/node/src/node_map.cpp
+++ b/platform/node/src/node_map.cpp
@@ -360,8 +360,7 @@ void NodeMap::renderFinished() {
         cb->Call(1, argv);
     } else if (img) {
         v8::Local<v8::Object> pixels = Nan::NewBuffer(
-            reinterpret_cast<char *>(img->pixels.get()),
-            size_t(img->width) * size_t(img->height) * sizeof(mbgl::StillImage::Pixel),
+            reinterpret_cast<char *>(img->pixels.get()), img->width * img->height * 4,
 
             // Retain the StillImage object until the buffer is deleted.
             [](char *, void *hint) {
diff --git a/test/miscellaneous/bilinear.cpp b/test/miscellaneous/bilinear.cpp
index bdfb9d911..722e7265c 100644
--- a/test/miscellaneous/bilinear.cpp
+++ b/test/miscellaneous/bilinear.cpp
@@ -42,7 +42,7 @@ TEST(Bilinear, Scaling) {
     util::bilinearScale(srcData, srcSize, { 252, 380, 12, 12 }, dstData, dstSize, { 18, 90, 24, 24 }, false);
 
     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.png", util::compress_png(dstSize.x, dstSize.y, reinterpret_cast<uint8_t *>(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"));