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#include <mbgl/util/image.hpp>
#include <png.h>
#include <cassert>
#include <cstdlib>
std::string mbgl::util::compress_png(int width, int height, void *rgba, bool flip) {
png_voidp error_ptr = 0;
png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, error_ptr, NULL, NULL);
if (!png_ptr) {
fprintf(stderr, "Couldn't create png_ptr\n");
return "";
}
png_infop info_ptr = png_create_info_struct(png_ptr);
if (!png_ptr) {
png_destroy_write_struct(&png_ptr, (png_infopp)0);
fprintf(stderr, "Couldn't create info_ptr\n");
return "";
}
png_set_IHDR(png_ptr, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
jmp_buf *jmp_context = (jmp_buf *)png_get_error_ptr(png_ptr);
if (jmp_context) {
png_destroy_write_struct(&png_ptr, &info_ptr);
return "";
}
std::string result;
png_set_write_fn(png_ptr, &result, [](png_structp png_ptr, png_bytep data, png_size_t length) {
std::string *out = static_cast<std::string *>(png_get_io_ptr(png_ptr));
out->append(reinterpret_cast<char *>(data), length);
}, NULL);
struct ptrs {
ptrs(size_t count) : rows(new png_bytep[count]) {}
~ptrs() { delete[] rows; }
png_bytep *rows = nullptr;
} pointers(height);
for (int i = 0; i < height; i++) {
pointers.rows[flip ? height - 1 - i : i] = (png_bytep)((png_bytep)rgba + width * 4 * i);
}
png_set_rows(png_ptr, info_ptr, pointers.rows);
png_write_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
png_destroy_write_struct(&png_ptr, &info_ptr);
return result;
}
using namespace mbgl::util;
struct Buffer {
Buffer(const std::string& data)
: data(data.data()), length(data.size()) {}
const char *const data = 0;
const size_t length = 0;
size_t pos = 0;
};
void readCallback(png_structp png, png_bytep data, png_size_t length) {
Buffer *reader = static_cast<Buffer *>(png_get_io_ptr(png));
// Read `length` bytes into `data`.
if (reader->pos + length > reader->length) {
png_error(png, "Read Error");
} else {
memcpy(data, reader->data + reader->pos, length);
reader->pos += length;
}
}
void errorHandler(png_structp, png_const_charp error_msg) {
throw std::runtime_error(error_msg);
}
void warningHandler(png_structp, png_const_charp error_msg) {
fprintf(stderr, "PNG: %s\n", error_msg);
}
Image::Image(const std::string &data, bool flip) {
Buffer buffer(data);
if (buffer.length < 8 || !png_check_sig((const png_bytep)buffer.data, 8)) {
fprintf(stderr, "image is not a valid PNG image\n");
return;
}
png_structp png = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, errorHandler, warningHandler);
assert(png);
png_infop info = png_create_info_struct(png);
assert(info);
int depth, color, interlace;
try {
png_set_read_fn(png, (png_voidp)&buffer, readCallback);
png_read_info(png, info);
png_get_IHDR(png, info, (png_uint_32*)&width, (png_uint_32*)&height, &depth, &color, &interlace, nullptr, nullptr);
bool alpha = (color & PNG_COLOR_MASK_ALPHA) || png_get_valid(png, info, PNG_INFO_tRNS);
// From http://trac.mapnik.org/browser/trunk/src/png_reader.cpp
if (color == PNG_COLOR_TYPE_PALETTE)
png_set_expand(png);
if (color == PNG_COLOR_TYPE_GRAY)
png_set_expand(png);
if (png_get_valid(png, info, PNG_INFO_tRNS))
png_set_expand(png);
if (depth == 16)
png_set_strip_16(png);
if (depth < 8)
png_set_packing(png);
if (color == PNG_COLOR_TYPE_GRAY ||
color == PNG_COLOR_TYPE_GRAY_ALPHA)
png_set_gray_to_rgb(png);
if (interlace == PNG_INTERLACE_ADAM7)
png_set_interlace_handling(png);
// Always add an alpha channel.
if (!alpha) {
png_set_add_alpha(png, 0xFF, PNG_FILLER_AFTER);
}
double gamma;
if (png_get_gAMA(png, info, &gamma))
png_set_gamma(png, 2.2, gamma);
png_read_update_info(png, info);
png_size_t rowbytes = png_get_rowbytes(png, info);
assert(width * 4 == rowbytes);
img = (char *)std::malloc(width * height * 4);
char *surface = img;
assert(surface);
struct ptrs {
ptrs(size_t count) : rows(new png_bytep[count]) {}
~ptrs() { delete[] rows; }
png_bytep *rows = nullptr;
} pointers(height);
for (unsigned i = 0; i < height; ++i) {
pointers.rows[flip ? height - 1 - i : i] = (png_bytep)(surface + (i * rowbytes));
}
// Read image data
png_read_image(png, pointers.rows);
png_read_end(png, nullptr);
png_destroy_read_struct(&png, &info, nullptr);
} catch (std::exception& e) {
fprintf(stderr, "loading PNG failed: %s\n", e.what());
png_destroy_read_struct(&png, &info, nullptr);
if (img) {
std::free(img);
img = nullptr;
}
width = 0;
height = 0;
}
}
Image::~Image() {
if (img) {
std::free(img);
img = nullptr;
}
}
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