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add image_reader abstraction layer to hanfle multiple image formats

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(work-in-progress)
This commit is contained in:
artemp
2014-11-07 11:49:31 +00:00
committed by Leith Bade
parent 90480ee58c
commit ae2d4e740e
9 changed files with 884 additions and 113 deletions
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128
platform/default/image.cpp
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@@ -8,7 +8,7 @@
#include <cstdlib>
#include <stdexcept>
#include <cstring>
#include <mbgl/util/image_reader.hpp>
// Check png library version.
const static bool png_version_check = []() {
@@ -73,121 +73,23 @@ std::string compress_png(int width, int height, void *rgba) {
return result;
}
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 {
std::memcpy(data, reader->data + reader->pos, length);
reader->pos += length;
}
}
void errorHandler(png_structp, png_const_charp error_msg) {
Log::Error(Event::Image, "PNG: %s", error_msg);
throw std::runtime_error(error_msg);
}
void warningHandler(png_structp, png_const_charp error_msg) {
Log::Warning(Event::General, "PNG: %s", error_msg);
}
Image::Image(const std::string &data) {
Buffer buffer(data);
if (buffer.length < 8 || !png_check_sig((const png_bytep)buffer.data, 8)) {
Log::Error(Event::Image, "image is not a valid PNG image");
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);
}
// FIXME work around gamma crash
double gamma;
if (png_get_gAMA(png, info, &gamma))
png_set_gamma(png, 2.2, gamma);
png_set_alpha_mode(png, PNG_ALPHA_PREMULTIPLIED, 2.2);
png_read_update_info(png, info);
png_size_t rowbytes = png_get_rowbytes(png, info);
assert(width * 4 == rowbytes);
Image::Image(std::string const& data)
{
try
{
std::unique_ptr<image_reader> reader(get_image_reader(data.c_str(), data.size()));
width = reader->width();
height = reader->height();
img = ::std::unique_ptr<char[]>(new char[width * height * 4]());
char *surface = img.get();
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[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) {
Log::Error(Event::Image, "loading PNG failed: %s", e.what());
png_destroy_read_struct(&png, &info, nullptr);
if (img) {
img.reset();
}
reader->read(0, 0, width, height, img.get());
}
catch (image_reader_exception const& ex)
{
fprintf(stderr, "ImageReader: %s\n", ex.what());
img.reset();
width = 0;
height = 0;
}
}