127 lines
4.4 KiB
C
127 lines
4.4 KiB
C
/*
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* png-reader.c
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* Copyright (C) 2018 Kovid Goyal <kovid at kovidgoyal.net>
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*
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* Distributed under terms of the GPL3 license.
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*/
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#include "png-reader.h"
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struct fake_file { const uint8_t *buf; size_t sz, cur; };
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static void
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read_png_from_buffer(png_structp png, png_bytep out, png_size_t length) {
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struct fake_file *f = png_get_io_ptr(png);
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if (f) {
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size_t amt = MIN(length, f->sz - f->cur);
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memcpy(out, f->buf + f->cur, amt);
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f->cur += amt;
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}
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}
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struct custom_error_handler {
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jmp_buf jb;
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png_error_handler_func err_handler;
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};
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static void
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read_png_error_handler(png_structp png_ptr, png_const_charp msg) {
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struct custom_error_handler *eh;
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eh = png_get_error_ptr(png_ptr);
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if (eh == NULL) fatal("read_png_error_handler: could not retrieve error handler");
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if(eh->err_handler) eh->err_handler("EBADPNG", msg);
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longjmp(eh->jb, 1);
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}
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static void
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read_png_warn_handler(png_structp UNUSED png_ptr, png_const_charp UNUSED msg) {
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// ignore warnings
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}
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#define ABRT(code, msg) { if(d->err_handler) d->err_handler(#code, msg); goto err; }
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void
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inflate_png_inner(png_read_data *d, const uint8_t *buf, size_t bufsz) {
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struct fake_file f = {.buf = buf, .sz = bufsz};
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png_structp png = NULL;
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png_infop info = NULL;
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struct custom_error_handler eh = {.err_handler = d->err_handler};
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png = png_create_read_struct(PNG_LIBPNG_VER_STRING, &eh, read_png_error_handler, read_png_warn_handler);
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if (!png) ABRT(ENOMEM, "Failed to create PNG read structure");
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info = png_create_info_struct(png);
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if (!info) ABRT(ENOMEM, "Failed to create PNG info structure");
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if (setjmp(eh.jb)) goto err;
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png_set_read_fn(png, &f, read_png_from_buffer);
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png_read_info(png, info);
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png_byte color_type, bit_depth;
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d->width = png_get_image_width(png, info);
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d->height = png_get_image_height(png, info);
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color_type = png_get_color_type(png, info);
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bit_depth = png_get_bit_depth(png, info);
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// Ensure we get RGBA data out of libpng
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if (bit_depth == 16) png_set_strip_16(png);
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if (color_type == PNG_COLOR_TYPE_PALETTE) png_set_palette_to_rgb(png);
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// PNG_COLOR_TYPE_GRAY_ALPHA is always 8 or 16bit depth.
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if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png);
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if (png_get_valid(png, info, PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png);
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// These color_type don't have an alpha channel then fill it with 0xff.
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if (color_type == PNG_COLOR_TYPE_RGB || color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_PALETTE) png_set_filler(png, 0xFF, PNG_FILLER_AFTER);
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if (color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_GRAY_ALPHA) png_set_gray_to_rgb(png);
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png_read_update_info(png, info);
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int rowbytes = png_get_rowbytes(png, info);
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d->sz = rowbytes * d->height * sizeof(png_byte);
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d->decompressed = malloc(d->sz + 16);
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if (d->decompressed == NULL) ABRT(ENOMEM, "Out of memory allocating decompression buffer for PNG");
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d->row_pointers = malloc(d->height * sizeof(png_bytep));
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if (d->row_pointers == NULL) ABRT(ENOMEM, "Out of memory allocating row_pointers buffer for PNG");
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for (int i = 0; i < d->height; i++) d->row_pointers[i] = d->decompressed + i * rowbytes;
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png_read_image(png, d->row_pointers);
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d->ok = true;
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err:
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if (png) png_destroy_read_struct(&png, info ? &info : NULL, NULL);
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return;
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}
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static void
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png_error_handler(const char *code, const char *msg) {
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PyErr_Format(PyExc_ValueError, "[%s] %s", code, msg);
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}
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static PyObject*
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load_png_data(PyObject *self UNUSED, PyObject *args) {
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Py_ssize_t sz;
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const char *data;
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if (!PyArg_ParseTuple(args, "s#", &data, &sz)) return NULL;
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png_read_data d = {.err_handler=png_error_handler};
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inflate_png_inner(&d, (const uint8_t*)data, sz);
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PyObject *ans = NULL;
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if (d.ok && !PyErr_Occurred()) {
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ans = Py_BuildValue("y#ii", d.decompressed, (int)d.sz, d.width, d.height);
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} else {
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if (!PyErr_Occurred()) PyErr_SetString(PyExc_ValueError, "Unknown error while reading PNG data");
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}
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free(d.decompressed);
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free(d.row_pointers);
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return ans;
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}
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static PyMethodDef module_methods[] = {
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METHODB(load_png_data, METH_VARARGS),
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{NULL, NULL, 0, NULL} /* Sentinel */
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};
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bool
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init_png_reader(PyObject *module) {
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if (PyModule_AddFunctions(module, module_methods) != 0) return false;
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return true;
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}
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