rcpp_framework/modules/image_png/png_driver_common.cpp

/*************************************************************************/
/*  png_driver_common.cpp                                                */
/*************************************************************************/
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#include "png_driver_common.h"

#include <png.h>
#include <string.h>

namespace PNGDriverCommon {

// Print any warnings.
// On error, set explain and return true.
// Call should be wrapped in ERR_FAIL_COND
static bool check_error(const png_image &image) {
	const png_uint_32 failed = PNG_IMAGE_FAILED(image);
	if (failed & PNG_IMAGE_ERROR) {
		return true;
	} else if (failed) {
		RPRINT_ERR(image.message);
	}
	return false;
}

Error png_to_image(const uint8_t *p_source, size_t p_size, bool p_force_linear, Ref<Image> p_image) {
	png_image png_img;
	memset(&png_img, 0, sizeof(png_img));
	png_img.version = PNG_IMAGE_VERSION;

	// fetch image properties
	int success = png_image_begin_read_from_memory(&png_img, p_source, p_size);
	ERR_FAIL_COND_V_MSG(check_error(png_img), ERR_FILE_CORRUPT, png_img.message);
	ERR_FAIL_COND_V(!success, ERR_FILE_CORRUPT);

	// flags to be masked out of input format to give target format
	const png_uint_32 format_mask = ~(
			// convert component order to RGBA
			PNG_FORMAT_FLAG_BGR | PNG_FORMAT_FLAG_AFIRST
			// convert 16 bit components to 8 bit
			| PNG_FORMAT_FLAG_LINEAR
			// convert indexed image to direct color
			| PNG_FORMAT_FLAG_COLORMAP);

	png_img.format &= format_mask;

	Image::Format dest_format;
	switch (png_img.format) {
		case PNG_FORMAT_GRAY:
			dest_format = Image::FORMAT_L8;
			break;
		case PNG_FORMAT_GA:
			dest_format = Image::FORMAT_LA8;
			break;
		case PNG_FORMAT_RGB:
			dest_format = Image::FORMAT_RGB8;
			break;
		case PNG_FORMAT_RGBA:
			dest_format = Image::FORMAT_RGBA8;
			break;
		default:
			png_image_free(&png_img); // only required when we return before finish_read
			RPRINT_ERR("Unsupported png format.");
			return ERR_UNAVAILABLE;
	}

	if (!p_force_linear) {
		// assume 16 bit pngs without sRGB or gAMA chunks are in sRGB format
		png_img.flags |= PNG_IMAGE_FLAG_16BIT_sRGB;
	}

	const png_uint_32 stride = PNG_IMAGE_ROW_STRIDE(png_img);
	Vector<uint8_t> buffer;
	buffer.resize(PNG_IMAGE_BUFFER_SIZE(png_img, stride));

	uint8_t *w = buffer.dataw();

	// read image data to buffer and release libpng resources
	success = png_image_finish_read(&png_img, nullptr, w, stride, nullptr);
	ERR_FAIL_COND_V_MSG(check_error(png_img), ERR_FILE_CORRUPT, png_img.message);
	ERR_FAIL_COND_V(!success, ERR_FILE_CORRUPT);

	p_image->create(png_img.width, png_img.height, false, dest_format, buffer);

	return OK;
}

Error image_to_png(const Ref<Image> &p_image, Vector<uint8_t> &p_buffer) {
	Ref<Image> source_image = p_image->duplicate();

	if (source_image->is_compressed()) {
		RPRINT_ERR("Can't handle compressed image!");
		return Error::ERR_INVALID_DATA;
	}

	ERR_FAIL_COND_V(source_image->is_compressed(), FAILED);

	png_image png_img;
	memset(&png_img, 0, sizeof(png_img));
	png_img.version = PNG_IMAGE_VERSION;
	png_img.width = source_image->get_width();
	png_img.height = source_image->get_height();

	switch (source_image->get_format()) {
		case Image::FORMAT_L8:
			png_img.format = PNG_FORMAT_GRAY;
			break;
		case Image::FORMAT_LA8:
			png_img.format = PNG_FORMAT_GA;
			break;
		case Image::FORMAT_RGB8:
			png_img.format = PNG_FORMAT_RGB;
			break;
		case Image::FORMAT_RGBA8:
			png_img.format = PNG_FORMAT_RGBA;
			break;
		default:
			if (source_image->detect_alpha()) {
				source_image->convert(Image::FORMAT_RGBA8);
				png_img.format = PNG_FORMAT_RGBA;
			} else {
				source_image->convert(Image::FORMAT_RGB8);
				png_img.format = PNG_FORMAT_RGB;
			}
	}

	const uint8_t *reader = source_image->datar();

	// we may be passed a buffer with existing content we're expected to append to
	const int buffer_offset = p_buffer.size();

	const size_t png_size_estimate = PNG_IMAGE_PNG_SIZE_MAX(png_img);

	// try with estimated size
	size_t compressed_size = png_size_estimate;
	int success = 0;
	{ // scope writer lifetime
		p_buffer.resize(buffer_offset + png_size_estimate);

		uint8_t* writer = p_buffer.dataw();
		success = png_image_write_to_memory(&png_img, &writer[buffer_offset],
				&compressed_size, 0, reader, 0, nullptr);
		ERR_FAIL_COND_V_MSG(check_error(png_img), FAILED, png_img.message);
	}

	if (!success) {
		// buffer was big enough, must be some other error
		ERR_FAIL_COND_V(compressed_size <= png_size_estimate, FAILED);

		// write failed due to buffer size, resize and retry
		p_buffer.resize(buffer_offset + compressed_size);

		uint8_t* writer = p_buffer.dataw();
		success = png_image_write_to_memory(&png_img, &writer[buffer_offset], &compressed_size, 0, reader, 0, nullptr);
		ERR_FAIL_COND_V_MSG(check_error(png_img), FAILED, png_img.message);
		ERR_FAIL_COND_V(!success, FAILED);
	}

	// trim buffer size to content
	p_buffer.resize(buffer_offset + compressed_size);

	return OK;
}

} // namespace PNGDriverCommon