blob: 5c904cf4ad15c3e43a8a9b75c3979360cd480f80 [file] [log] [blame]
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
#include "config.h"
#include "log.h"
#include "png.h"
#include <cairo/cairo.h>
#include <stdlib.h>
#include <string.h>
* The current state of the PNG decoder.
typedef struct guacenc_png_read_state {
* The buffer of unread image data. This pointer will be updated to point
* to the next unread byte when data is read.
unsigned char* data;
* The number of bytes remaining to be read within the buffer.
unsigned int length;
} guacenc_png_read_state;
* Attempts to fill the given buffer with read image data. The behavior of
* this function is dictated by cairo_read_t.
* @param closure
* The current state of the PNG decoding process (an instance of
* guacenc_png_read_state).
* @param data
* The data buffer to fill.
* @param length
* The number of bytes to fill within the data buffer.
* @return
* CAIRO_STATUS_SUCCESS if all data was read successfully (the entire
* buffer was filled), CAIRO_STATUS_READ_ERROR otherwise.
static cairo_status_t guacenc_png_read(void* closure, unsigned char* data,
unsigned int length) {
guacenc_png_read_state* state = (guacenc_png_read_state*) closure;
/* If more data is requested than is available in buffer, fail */
if (length > state->length)
/* Read chunk into buffer */
memcpy(data, state->data, length);
/* Advance to next chunk */
state->length -= length;
state->data += length;
/* Read was successful */
cairo_surface_t* guacenc_png_decoder(unsigned char* data, int length) {
guacenc_png_read_state state = {
.data = data,
.length = length
/* Read PNG from data */
cairo_surface_t* surface =
cairo_image_surface_create_from_png_stream(guacenc_png_read, &state);
/* If surface returned with an error, just return NULL */
if (surface != NULL &&
cairo_surface_status(surface) != CAIRO_STATUS_SUCCESS) {
guacenc_log(GUAC_LOG_WARNING, "Invalid PNG data");
return NULL;
/* PNG was read successfully */
return surface;