1 #include <mbgl/util/image.hpp>
2 #include <mbgl/util/premultiply.hpp>
3 #include <mbgl/util/char_array_buffer.hpp>
4 #include <mbgl/util/logging.hpp>
5
6 #include <istream>
7 #include <sstream>
8
9 extern "C"
10 {
11 #include <png.h>
12 }
13
14 template<size_t max, typename... Args>
sprintf(const char * msg,Args...args)15 static std::string sprintf(const char *msg, Args... args) {
16 char res[max];
17 int len = snprintf(res, sizeof(res), msg, args...);
18 return std::string(res, len);
19 }
20
__anon9c775e750102() 21 const static bool png_version_check __attribute__((unused)) = []() {
22 const png_uint_32 version = png_access_version_number();
23 if (version != PNG_LIBPNG_VER) {
24 throw std::runtime_error(sprintf<96>(
25 "libpng version mismatch: headers report %d.%d.%d, but library reports %d.%d.%d",
26 PNG_LIBPNG_VER / 10000, (PNG_LIBPNG_VER / 100) % 100, PNG_LIBPNG_VER % 100,
27 version / 10000, (version / 100) % 100, version % 100));
28 }
29 return true;
30 }();
31
32 namespace mbgl {
33
user_error_fn(png_structp,png_const_charp error_msg)34 static void user_error_fn(png_structp, png_const_charp error_msg) {
35 throw std::runtime_error(std::string("failed to read invalid png: '") + error_msg + "'");
36 }
37
user_warning_fn(png_structp,png_const_charp warning_msg)38 static void user_warning_fn(png_structp, png_const_charp warning_msg) {
39 Log::Warning(Event::Image, "ImageReader (PNG): %s", warning_msg);
40 }
41
png_read_data(png_structp png_ptr,png_bytep data,png_size_t length)42 static void png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) {
43 auto* fin = reinterpret_cast<std::istream*>(png_get_io_ptr(png_ptr));
44 fin->read(reinterpret_cast<char*>(data), length);
45 std::streamsize read_count = fin->gcount();
46 if (read_count < 0 || static_cast<png_size_t>(read_count) != length)
47 {
48 png_error(png_ptr, "Read Error");
49 }
50 }
51
52 struct png_struct_guard {
png_struct_guardmbgl::png_struct_guard53 png_struct_guard(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr)
54 : p_(png_ptr_ptr),
55 i_(info_ptr_ptr) {}
56
~png_struct_guardmbgl::png_struct_guard57 ~png_struct_guard() {
58 png_destroy_read_struct(p_,i_,nullptr);
59 }
60
61 png_structpp p_;
62 png_infopp i_;
63 };
64
decodePNG(const uint8_t * data,size_t size)65 PremultipliedImage decodePNG(const uint8_t* data, size_t size) {
66 util::CharArrayBuffer dataBuffer { reinterpret_cast<const char*>(data), size };
67 std::istream stream(&dataBuffer);
68
69 png_byte header[8] = { 0 };
70 stream.read(reinterpret_cast<char*>(header), 8);
71 if (stream.gcount() != 8)
72 throw std::runtime_error("PNG reader: Could not read image");
73
74 int is_png = !png_sig_cmp(header, 0, 8);
75 if (!is_png)
76 throw std::runtime_error("File or stream is not a png");
77
78 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
79 if (!png_ptr)
80 throw std::runtime_error("failed to allocate png_ptr");
81
82 // catch errors in a custom way to avoid the need for setjmp
83 png_set_error_fn(png_ptr, png_get_error_ptr(png_ptr), user_error_fn, user_warning_fn);
84
85 png_infop info_ptr;
86 png_struct_guard sguard(&png_ptr, &info_ptr);
87 info_ptr = png_create_info_struct(png_ptr);
88 if (!info_ptr)
89 throw std::runtime_error("failed to create info_ptr");
90
91 png_set_read_fn(png_ptr, &stream, png_read_data);
92 png_set_sig_bytes(png_ptr, 8);
93 png_read_info(png_ptr, info_ptr);
94
95 png_uint_32 width = 0;
96 png_uint_32 height = 0;
97 int bit_depth = 0;
98 int color_type = 0;
99 png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, nullptr, nullptr, nullptr);
100
101 UnassociatedImage image({ static_cast<uint32_t>(width), static_cast<uint32_t>(height) });
102
103 if (color_type == PNG_COLOR_TYPE_PALETTE)
104 png_set_expand(png_ptr);
105
106 if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
107 png_set_expand(png_ptr);
108
109 if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
110 png_set_expand(png_ptr);
111
112 if (bit_depth == 16)
113 png_set_strip_16(png_ptr);
114
115 if (color_type == PNG_COLOR_TYPE_GRAY ||
116 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
117 png_set_gray_to_rgb(png_ptr);
118
119 png_set_add_alpha(png_ptr, 0xff, PNG_FILLER_AFTER);
120
121 if (png_get_interlace_type(png_ptr,info_ptr) == PNG_INTERLACE_ADAM7) {
122 png_set_interlace_handling(png_ptr); // FIXME: libpng bug?
123 // according to docs png_read_image
124 // "..automatically handles interlacing,
125 // so you don't need to call png_set_interlace_handling()"
126 }
127
128 png_read_update_info(png_ptr, info_ptr);
129
130 // we can read whole image at once
131 // alloc row pointers
132 const std::unique_ptr<png_bytep[]> rows(new png_bytep[height]);
133 for (unsigned row = 0; row < height; ++row)
134 rows[row] = image.data.get() + row * width * 4;
135 png_read_image(png_ptr, rows.get());
136
137 png_read_end(png_ptr, nullptr);
138
139 return util::premultiply(std::move(image));
140 }
141
142 } // namespace mbgl
143