Revert^2 "Move some image/9patch code to androidfw"
This reverts commit 917043bc2586743afda5a21386893fa8c787800b.
Reason for revert: Roll forward with fix
Test: Automatic
Bug: 296324826
Change-Id: I42a0b48c02fd497b2174c0c65f300265202f7ab1
diff --git a/libs/androidfw/PngCrunch.cpp b/libs/androidfw/PngCrunch.cpp
new file mode 100644
index 0000000..cf3c0ee
--- /dev/null
+++ b/libs/androidfw/PngCrunch.cpp
@@ -0,0 +1,730 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed 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
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <png.h>
+#include <zlib.h>
+
+#include <algorithm>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "android-base/errors.h"
+#include "android-base/logging.h"
+#include "android-base/macros.h"
+#include "androidfw/Png.h"
+
+namespace android {
+
+// Custom deleter that destroys libpng read and info structs.
+class PngReadStructDeleter {
+ public:
+ PngReadStructDeleter(png_structp read_ptr, png_infop info_ptr)
+ : read_ptr_(read_ptr), info_ptr_(info_ptr) {
+ }
+
+ ~PngReadStructDeleter() {
+ png_destroy_read_struct(&read_ptr_, &info_ptr_, nullptr);
+ }
+
+ private:
+ png_structp read_ptr_;
+ png_infop info_ptr_;
+
+ DISALLOW_COPY_AND_ASSIGN(PngReadStructDeleter);
+};
+
+// Custom deleter that destroys libpng write and info structs.
+class PngWriteStructDeleter {
+ public:
+ PngWriteStructDeleter(png_structp write_ptr, png_infop info_ptr)
+ : write_ptr_(write_ptr), info_ptr_(info_ptr) {
+ }
+
+ ~PngWriteStructDeleter() {
+ png_destroy_write_struct(&write_ptr_, &info_ptr_);
+ }
+
+ private:
+ png_structp write_ptr_;
+ png_infop info_ptr_;
+
+ DISALLOW_COPY_AND_ASSIGN(PngWriteStructDeleter);
+};
+
+// Custom warning logging method that uses IDiagnostics.
+static void LogWarning(png_structp png_ptr, png_const_charp warning_msg) {
+ android::IDiagnostics* diag = (android::IDiagnostics*)png_get_error_ptr(png_ptr);
+ diag->Warn(android::DiagMessage() << warning_msg);
+}
+
+// Custom error logging method that uses IDiagnostics.
+static void LogError(png_structp png_ptr, png_const_charp error_msg) {
+ android::IDiagnostics* diag = (android::IDiagnostics*)png_get_error_ptr(png_ptr);
+ diag->Error(android::DiagMessage() << error_msg);
+
+ // Causes libpng to longjmp to the spot where setjmp was set. This is how libpng does
+ // error handling. If this custom error handler method were to return, libpng would, by
+ // default, print the error message to stdout and call the same png_longjmp method.
+ png_longjmp(png_ptr, 1);
+}
+
+static void ReadDataFromStream(png_structp png_ptr, png_bytep buffer, png_size_t len) {
+ InputStream* in = (InputStream*)png_get_io_ptr(png_ptr);
+
+ const void* in_buffer;
+ size_t in_len;
+ if (!in->Next(&in_buffer, &in_len)) {
+ if (in->HadError()) {
+ std::stringstream error_msg_builder;
+ error_msg_builder << "failed reading from input";
+ if (!in->GetError().empty()) {
+ error_msg_builder << ": " << in->GetError();
+ }
+ std::string err = error_msg_builder.str();
+ png_error(png_ptr, err.c_str());
+ }
+ return;
+ }
+
+ const size_t bytes_read = std::min(in_len, len);
+ memcpy(buffer, in_buffer, bytes_read);
+ if (bytes_read != in_len) {
+ in->BackUp(in_len - bytes_read);
+ }
+}
+
+static void WriteDataToStream(png_structp png_ptr, png_bytep buffer, png_size_t len) {
+ OutputStream* out = (OutputStream*)png_get_io_ptr(png_ptr);
+
+ void* out_buffer;
+ size_t out_len;
+ while (len > 0) {
+ if (!out->Next(&out_buffer, &out_len)) {
+ if (out->HadError()) {
+ std::stringstream err_msg_builder;
+ err_msg_builder << "failed writing to output";
+ if (!out->GetError().empty()) {
+ err_msg_builder << ": " << out->GetError();
+ }
+ std::string err = out->GetError();
+ png_error(png_ptr, err.c_str());
+ }
+ return;
+ }
+
+ const size_t bytes_written = std::min(out_len, len);
+ memcpy(out_buffer, buffer, bytes_written);
+
+ // Advance the input buffer.
+ buffer += bytes_written;
+ len -= bytes_written;
+
+ // Advance the output buffer.
+ out_len -= bytes_written;
+ }
+
+ // If the entire output buffer wasn't used, backup.
+ if (out_len > 0) {
+ out->BackUp(out_len);
+ }
+}
+
+std::unique_ptr<Image> ReadPng(InputStream* in, IDiagnostics* diag) {
+ // Read the first 8 bytes of the file looking for the PNG signature.
+ // Bail early if it does not match.
+ const png_byte* signature;
+ size_t buffer_size;
+ if (!in->Next((const void**)&signature, &buffer_size)) {
+ if (in->HadError()) {
+ diag->Error(android::DiagMessage() << "failed to read PNG signature: " << in->GetError());
+ } else {
+ diag->Error(android::DiagMessage() << "not enough data for PNG signature");
+ }
+ return {};
+ }
+
+ if (buffer_size < kPngSignatureSize || png_sig_cmp(signature, 0, kPngSignatureSize) != 0) {
+ diag->Error(android::DiagMessage() << "file signature does not match PNG signature");
+ return {};
+ }
+
+ // Start at the beginning of the first chunk.
+ in->BackUp(buffer_size - kPngSignatureSize);
+
+ // Create and initialize the png_struct with the default error and warning handlers.
+ // The header version is also passed in to ensure that this was built against the same
+ // version of libpng.
+ png_structp read_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
+ if (read_ptr == nullptr) {
+ diag->Error(android::DiagMessage() << "failed to create libpng read png_struct");
+ return {};
+ }
+
+ // Create and initialize the memory for image header and data.
+ png_infop info_ptr = png_create_info_struct(read_ptr);
+ if (info_ptr == nullptr) {
+ diag->Error(android::DiagMessage() << "failed to create libpng read png_info");
+ png_destroy_read_struct(&read_ptr, nullptr, nullptr);
+ return {};
+ }
+
+ // Automatically release PNG resources at end of scope.
+ PngReadStructDeleter png_read_deleter(read_ptr, info_ptr);
+
+ // libpng uses longjmp to jump to an error handling routine.
+ // setjmp will only return true if it was jumped to, aka there was
+ // an error.
+ if (setjmp(png_jmpbuf(read_ptr))) {
+ return {};
+ }
+
+ // Handle warnings ourselves via IDiagnostics.
+ png_set_error_fn(read_ptr, (png_voidp)&diag, LogError, LogWarning);
+
+ // Set up the read functions which read from our custom data sources.
+ png_set_read_fn(read_ptr, (png_voidp)in, ReadDataFromStream);
+
+ // Skip the signature that we already read.
+ png_set_sig_bytes(read_ptr, kPngSignatureSize);
+
+ // Read the chunk headers.
+ png_read_info(read_ptr, info_ptr);
+
+ // Extract image meta-data from the various chunk headers.
+ uint32_t width, height;
+ int bit_depth, color_type, interlace_method, compression_method, filter_method;
+ png_get_IHDR(read_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_method,
+ &compression_method, &filter_method);
+
+ // When the image is read, expand it so that it is in RGBA 8888 format
+ // so that image handling is uniform.
+
+ if (color_type == PNG_COLOR_TYPE_PALETTE) {
+ png_set_palette_to_rgb(read_ptr);
+ }
+
+ if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
+ png_set_expand_gray_1_2_4_to_8(read_ptr);
+ }
+
+ if (png_get_valid(read_ptr, info_ptr, PNG_INFO_tRNS)) {
+ png_set_tRNS_to_alpha(read_ptr);
+ }
+
+ if (bit_depth == 16) {
+ png_set_strip_16(read_ptr);
+ }
+
+ if (!(color_type & PNG_COLOR_MASK_ALPHA)) {
+ png_set_add_alpha(read_ptr, 0xFF, PNG_FILLER_AFTER);
+ }
+
+ if (color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
+ png_set_gray_to_rgb(read_ptr);
+ }
+
+ if (interlace_method != PNG_INTERLACE_NONE) {
+ png_set_interlace_handling(read_ptr);
+ }
+
+ // Once all the options for reading have been set, we need to flush
+ // them to libpng.
+ png_read_update_info(read_ptr, info_ptr);
+
+ // 9-patch uses int32_t to index images, so we cap the image dimensions to
+ // something
+ // that can always be represented by 9-patch.
+ if (width > std::numeric_limits<int32_t>::max() || height > std::numeric_limits<int32_t>::max()) {
+ diag->Error(android::DiagMessage()
+ << "PNG image dimensions are too large: " << width << "x" << height);
+ return {};
+ }
+
+ std::unique_ptr<Image> output_image = std::make_unique<Image>();
+ output_image->width = static_cast<int32_t>(width);
+ output_image->height = static_cast<int32_t>(height);
+
+ const size_t row_bytes = png_get_rowbytes(read_ptr, info_ptr);
+ CHECK(row_bytes == 4 * width); // RGBA
+
+ // Allocate one large block to hold the image.
+ output_image->data = std::unique_ptr<uint8_t[]>(new uint8_t[height * row_bytes]);
+
+ // Create an array of rows that index into the data block.
+ output_image->rows = std::unique_ptr<uint8_t*[]>(new uint8_t*[height]);
+ for (uint32_t h = 0; h < height; h++) {
+ output_image->rows[h] = output_image->data.get() + (h * row_bytes);
+ }
+
+ // Actually read the image pixels.
+ png_read_image(read_ptr, output_image->rows.get());
+
+ // Finish reading. This will read any other chunks after the image data.
+ png_read_end(read_ptr, info_ptr);
+
+ return output_image;
+}
+
+// Experimentally chosen constant to be added to the overhead of using color type
+// PNG_COLOR_TYPE_PALETTE to account for the uncompressability of the palette chunk.
+// Without this, many small PNGs encoded with palettes are larger after compression than
+// the same PNGs encoded as RGBA.
+constexpr static const size_t kPaletteOverheadConstant = 1024u * 10u;
+
+// Pick a color type by which to encode the image, based on which color type will take
+// the least amount of disk space.
+//
+// 9-patch images traditionally have not been encoded with palettes.
+// The original rationale was to avoid dithering until after scaling,
+// but I don't think this would be an issue with palettes. Either way,
+// our naive size estimation tends to be wrong for small images like 9-patches
+// and using palettes balloons the size of the resulting 9-patch.
+// In order to not regress in size, restrict 9-patch to not use palettes.
+
+// The options are:
+//
+// - RGB
+// - RGBA
+// - RGB + cheap alpha
+// - Color palette
+// - Color palette + cheap alpha
+// - Color palette + alpha palette
+// - Grayscale
+// - Grayscale + cheap alpha
+// - Grayscale + alpha
+//
+static int PickColorType(int32_t width, int32_t height, bool grayscale,
+ bool convertible_to_grayscale, bool has_nine_patch,
+ size_t color_palette_size, size_t alpha_palette_size) {
+ const size_t palette_chunk_size = 16 + color_palette_size * 3;
+ const size_t alpha_chunk_size = 16 + alpha_palette_size;
+ const size_t color_alpha_data_chunk_size = 16 + 4 * width * height;
+ const size_t color_data_chunk_size = 16 + 3 * width * height;
+ const size_t grayscale_alpha_data_chunk_size = 16 + 2 * width * height;
+ const size_t palette_data_chunk_size = 16 + width * height;
+
+ if (grayscale) {
+ if (alpha_palette_size == 0) {
+ // This is the smallest the data can be.
+ return PNG_COLOR_TYPE_GRAY;
+ } else if (color_palette_size <= 256 && !has_nine_patch) {
+ // This grayscale has alpha and can fit within a palette.
+ // See if it is worth fitting into a palette.
+ const size_t palette_threshold = palette_chunk_size + alpha_chunk_size +
+ palette_data_chunk_size + kPaletteOverheadConstant;
+ if (grayscale_alpha_data_chunk_size > palette_threshold) {
+ return PNG_COLOR_TYPE_PALETTE;
+ }
+ }
+ return PNG_COLOR_TYPE_GRAY_ALPHA;
+ }
+
+ if (color_palette_size <= 256 && !has_nine_patch) {
+ // This image can fit inside a palette. Let's see if it is worth it.
+ size_t total_size_with_palette = palette_data_chunk_size + palette_chunk_size;
+ size_t total_size_without_palette = color_data_chunk_size;
+ if (alpha_palette_size > 0) {
+ total_size_with_palette += alpha_palette_size;
+ total_size_without_palette = color_alpha_data_chunk_size;
+ }
+
+ if (total_size_without_palette > total_size_with_palette + kPaletteOverheadConstant) {
+ return PNG_COLOR_TYPE_PALETTE;
+ }
+ }
+
+ if (convertible_to_grayscale) {
+ if (alpha_palette_size == 0) {
+ return PNG_COLOR_TYPE_GRAY;
+ } else {
+ return PNG_COLOR_TYPE_GRAY_ALPHA;
+ }
+ }
+
+ if (alpha_palette_size == 0) {
+ return PNG_COLOR_TYPE_RGB;
+ }
+ return PNG_COLOR_TYPE_RGBA;
+}
+
+// Assigns indices to the color and alpha palettes, encodes them, and then invokes
+// png_set_PLTE/png_set_tRNS.
+// This must be done before writing image data.
+// Image data must be transformed to use the indices assigned within the palette.
+static void WritePalette(png_structp write_ptr, png_infop write_info_ptr,
+ std::unordered_map<uint32_t, int>* color_palette,
+ std::unordered_set<uint32_t>* alpha_palette) {
+ CHECK(color_palette->size() <= 256);
+ CHECK(alpha_palette->size() <= 256);
+
+ // Populate the PNG palette struct and assign indices to the color palette.
+
+ // Colors in the alpha palette should have smaller indices.
+ // This will ensure that we can truncate the alpha palette if it is
+ // smaller than the color palette.
+ int index = 0;
+ for (uint32_t color : *alpha_palette) {
+ (*color_palette)[color] = index++;
+ }
+
+ // Assign the rest of the entries.
+ for (auto& entry : *color_palette) {
+ if (entry.second == -1) {
+ entry.second = index++;
+ }
+ }
+
+ // Create the PNG color palette struct.
+ auto color_palette_bytes = std::unique_ptr<png_color[]>(new png_color[color_palette->size()]);
+
+ std::unique_ptr<png_byte[]> alpha_palette_bytes;
+ if (!alpha_palette->empty()) {
+ alpha_palette_bytes = std::unique_ptr<png_byte[]>(new png_byte[alpha_palette->size()]);
+ }
+
+ for (const auto& entry : *color_palette) {
+ const uint32_t color = entry.first;
+ const int index = entry.second;
+ CHECK(index >= 0);
+ CHECK(static_cast<size_t>(index) < color_palette->size());
+
+ png_colorp slot = color_palette_bytes.get() + index;
+ slot->red = color >> 24;
+ slot->green = color >> 16;
+ slot->blue = color >> 8;
+
+ const png_byte alpha = color & 0x000000ff;
+ if (alpha != 0xff && alpha_palette_bytes) {
+ CHECK(static_cast<size_t>(index) < alpha_palette->size());
+ alpha_palette_bytes[index] = alpha;
+ }
+ }
+
+ // The bytes get copied here, so it is safe to release color_palette_bytes at
+ // the end of function
+ // scope.
+ png_set_PLTE(write_ptr, write_info_ptr, color_palette_bytes.get(), color_palette->size());
+
+ if (alpha_palette_bytes) {
+ png_set_tRNS(write_ptr, write_info_ptr, alpha_palette_bytes.get(), alpha_palette->size(),
+ nullptr);
+ }
+}
+
+// Write the 9-patch custom PNG chunks to write_info_ptr. This must be done
+// before writing image data.
+static void WriteNinePatch(png_structp write_ptr, png_infop write_info_ptr,
+ const NinePatch* nine_patch) {
+ // The order of the chunks is important.
+ // 9-patch code in older platforms expects the 9-patch chunk to be last.
+
+ png_unknown_chunk unknown_chunks[3];
+ memset(unknown_chunks, 0, sizeof(unknown_chunks));
+
+ size_t index = 0;
+ size_t chunk_len = 0;
+
+ std::unique_ptr<uint8_t[]> serialized_outline =
+ nine_patch->SerializeRoundedRectOutline(&chunk_len);
+ strcpy((char*)unknown_chunks[index].name, "npOl");
+ unknown_chunks[index].size = chunk_len;
+ unknown_chunks[index].data = (png_bytep)serialized_outline.get();
+ unknown_chunks[index].location = PNG_HAVE_PLTE;
+ index++;
+
+ std::unique_ptr<uint8_t[]> serialized_layout_bounds;
+ if (nine_patch->layout_bounds.nonZero()) {
+ serialized_layout_bounds = nine_patch->SerializeLayoutBounds(&chunk_len);
+ strcpy((char*)unknown_chunks[index].name, "npLb");
+ unknown_chunks[index].size = chunk_len;
+ unknown_chunks[index].data = (png_bytep)serialized_layout_bounds.get();
+ unknown_chunks[index].location = PNG_HAVE_PLTE;
+ index++;
+ }
+
+ std::unique_ptr<uint8_t[]> serialized_nine_patch = nine_patch->SerializeBase(&chunk_len);
+ strcpy((char*)unknown_chunks[index].name, "npTc");
+ unknown_chunks[index].size = chunk_len;
+ unknown_chunks[index].data = (png_bytep)serialized_nine_patch.get();
+ unknown_chunks[index].location = PNG_HAVE_PLTE;
+ index++;
+
+ // Handle all unknown chunks. We are manually setting the chunks here,
+ // so we will only ever handle our custom chunks.
+ png_set_keep_unknown_chunks(write_ptr, PNG_HANDLE_CHUNK_ALWAYS, nullptr, 0);
+
+ // Set the actual chunks here. The data gets copied, so our buffers can
+ // safely go out of scope.
+ png_set_unknown_chunks(write_ptr, write_info_ptr, unknown_chunks, index);
+}
+
+bool WritePng(const Image* image, const NinePatch* nine_patch, OutputStream* out,
+ const PngOptions& options, IDiagnostics* diag, bool verbose) {
+ // Create and initialize the write png_struct with the default error and
+ // warning handlers.
+ // The header version is also passed in to ensure that this was built against the same
+ // version of libpng.
+ png_structp write_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
+ if (write_ptr == nullptr) {
+ diag->Error(android::DiagMessage() << "failed to create libpng write png_struct");
+ return false;
+ }
+
+ // Allocate memory to store image header data.
+ png_infop write_info_ptr = png_create_info_struct(write_ptr);
+ if (write_info_ptr == nullptr) {
+ diag->Error(android::DiagMessage() << "failed to create libpng write png_info");
+ png_destroy_write_struct(&write_ptr, nullptr);
+ return false;
+ }
+
+ // Automatically release PNG resources at end of scope.
+ PngWriteStructDeleter png_write_deleter(write_ptr, write_info_ptr);
+
+ // libpng uses longjmp to jump to error handling routines.
+ // setjmp will return true only if it was jumped to, aka, there was an error.
+ if (setjmp(png_jmpbuf(write_ptr))) {
+ return false;
+ }
+
+ // Handle warnings with our IDiagnostics.
+ png_set_error_fn(write_ptr, (png_voidp)&diag, LogError, LogWarning);
+
+ // Set up the write functions which write to our custom data sources.
+ png_set_write_fn(write_ptr, (png_voidp)out, WriteDataToStream, nullptr);
+
+ // We want small files and can take the performance hit to achieve this goal.
+ png_set_compression_level(write_ptr, Z_BEST_COMPRESSION);
+
+ // Begin analysis of the image data.
+ // Scan the entire image and determine if:
+ // 1. Every pixel has R == G == B (grayscale)
+ // 2. Every pixel has A == 255 (opaque)
+ // 3. There are no more than 256 distinct RGBA colors (palette).
+ std::unordered_map<uint32_t, int> color_palette;
+ std::unordered_set<uint32_t> alpha_palette;
+ bool needs_to_zero_rgb_channels_of_transparent_pixels = false;
+ bool grayscale = true;
+ int max_gray_deviation = 0;
+
+ for (int32_t y = 0; y < image->height; y++) {
+ const uint8_t* row = image->rows[y];
+ for (int32_t x = 0; x < image->width; x++) {
+ int red = *row++;
+ int green = *row++;
+ int blue = *row++;
+ int alpha = *row++;
+
+ if (alpha == 0) {
+ // The color is completely transparent.
+ // For purposes of palettes and grayscale optimization,
+ // treat all channels as 0x00.
+ needs_to_zero_rgb_channels_of_transparent_pixels =
+ needs_to_zero_rgb_channels_of_transparent_pixels ||
+ (red != 0 || green != 0 || blue != 0);
+ red = green = blue = 0;
+ }
+
+ // Insert the color into the color palette.
+ const uint32_t color = red << 24 | green << 16 | blue << 8 | alpha;
+ color_palette[color] = -1;
+
+ // If the pixel has non-opaque alpha, insert it into the
+ // alpha palette.
+ if (alpha != 0xff) {
+ alpha_palette.insert(color);
+ }
+
+ // Check if the image is indeed grayscale.
+ if (grayscale) {
+ if (red != green || red != blue) {
+ grayscale = false;
+ }
+ }
+
+ // Calculate the gray scale deviation so that it can be compared
+ // with the threshold.
+ max_gray_deviation = std::max(std::abs(red - green), max_gray_deviation);
+ max_gray_deviation = std::max(std::abs(green - blue), max_gray_deviation);
+ max_gray_deviation = std::max(std::abs(blue - red), max_gray_deviation);
+ }
+ }
+
+ if (verbose) {
+ android::DiagMessage msg;
+ msg << " paletteSize=" << color_palette.size() << " alphaPaletteSize=" << alpha_palette.size()
+ << " maxGrayDeviation=" << max_gray_deviation
+ << " grayScale=" << (grayscale ? "true" : "false");
+ diag->Note(msg);
+ }
+
+ const bool convertible_to_grayscale = max_gray_deviation <= options.grayscale_tolerance;
+
+ const int new_color_type =
+ PickColorType(image->width, image->height, grayscale, convertible_to_grayscale,
+ nine_patch != nullptr, color_palette.size(), alpha_palette.size());
+
+ if (verbose) {
+ android::DiagMessage msg;
+ msg << "encoding PNG ";
+ if (nine_patch) {
+ msg << "(with 9-patch) as ";
+ }
+ switch (new_color_type) {
+ case PNG_COLOR_TYPE_GRAY:
+ msg << "GRAY";
+ break;
+ case PNG_COLOR_TYPE_GRAY_ALPHA:
+ msg << "GRAY + ALPHA";
+ break;
+ case PNG_COLOR_TYPE_RGB:
+ msg << "RGB";
+ break;
+ case PNG_COLOR_TYPE_RGB_ALPHA:
+ msg << "RGBA";
+ break;
+ case PNG_COLOR_TYPE_PALETTE:
+ msg << "PALETTE";
+ break;
+ default:
+ msg << "unknown type " << new_color_type;
+ break;
+ }
+ diag->Note(msg);
+ }
+
+ png_set_IHDR(write_ptr, write_info_ptr, image->width, image->height, 8, new_color_type,
+ PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
+
+ if (new_color_type & PNG_COLOR_MASK_PALETTE) {
+ // Assigns indices to the palette, and writes the encoded palette to the
+ // libpng writePtr.
+ WritePalette(write_ptr, write_info_ptr, &color_palette, &alpha_palette);
+ png_set_filter(write_ptr, 0, PNG_NO_FILTERS);
+ } else {
+ png_set_filter(write_ptr, 0, PNG_ALL_FILTERS);
+ }
+
+ if (nine_patch) {
+ WriteNinePatch(write_ptr, write_info_ptr, nine_patch);
+ }
+
+ // Flush our updates to the header.
+ png_write_info(write_ptr, write_info_ptr);
+
+ // Write out each row of image data according to its encoding.
+ if (new_color_type == PNG_COLOR_TYPE_PALETTE) {
+ // 1 byte/pixel.
+ auto out_row = std::unique_ptr<png_byte[]>(new png_byte[image->width]);
+
+ for (int32_t y = 0; y < image->height; y++) {
+ png_const_bytep in_row = image->rows[y];
+ for (int32_t x = 0; x < image->width; x++) {
+ int rr = *in_row++;
+ int gg = *in_row++;
+ int bb = *in_row++;
+ int aa = *in_row++;
+ if (aa == 0) {
+ // Zero out color channels when transparent.
+ rr = gg = bb = 0;
+ }
+
+ const uint32_t color = rr << 24 | gg << 16 | bb << 8 | aa;
+ const int idx = color_palette[color];
+ CHECK(idx != -1);
+ out_row[x] = static_cast<png_byte>(idx);
+ }
+ png_write_row(write_ptr, out_row.get());
+ }
+ } else if (new_color_type == PNG_COLOR_TYPE_GRAY || new_color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
+ const size_t bpp = new_color_type == PNG_COLOR_TYPE_GRAY ? 1 : 2;
+ auto out_row = std::unique_ptr<png_byte[]>(new png_byte[image->width * bpp]);
+
+ for (int32_t y = 0; y < image->height; y++) {
+ png_const_bytep in_row = image->rows[y];
+ for (int32_t x = 0; x < image->width; x++) {
+ int rr = in_row[x * 4];
+ int gg = in_row[x * 4 + 1];
+ int bb = in_row[x * 4 + 2];
+ int aa = in_row[x * 4 + 3];
+ if (aa == 0) {
+ // Zero out the gray channel when transparent.
+ rr = gg = bb = 0;
+ }
+
+ if (grayscale) {
+ // The image was already grayscale, red == green == blue.
+ out_row[x * bpp] = in_row[x * 4];
+ } else {
+ // The image is convertible to grayscale, use linear-luminance of
+ // sRGB colorspace:
+ // https://en.wikipedia.org/wiki/Grayscale#Colorimetric_.28luminance-preserving.29_conversion_to_grayscale
+ out_row[x * bpp] = (png_byte)(rr * 0.2126f + gg * 0.7152f + bb * 0.0722f);
+ }
+
+ if (bpp == 2) {
+ // Write out alpha if we have it.
+ out_row[x * bpp + 1] = aa;
+ }
+ }
+ png_write_row(write_ptr, out_row.get());
+ }
+ } else if (new_color_type == PNG_COLOR_TYPE_RGB || new_color_type == PNG_COLOR_TYPE_RGBA) {
+ const size_t bpp = new_color_type == PNG_COLOR_TYPE_RGB ? 3 : 4;
+ if (needs_to_zero_rgb_channels_of_transparent_pixels) {
+ // The source RGBA data can't be used as-is, because we need to zero out
+ // the RGB values of transparent pixels.
+ auto out_row = std::unique_ptr<png_byte[]>(new png_byte[image->width * bpp]);
+
+ for (int32_t y = 0; y < image->height; y++) {
+ png_const_bytep in_row = image->rows[y];
+ for (int32_t x = 0; x < image->width; x++) {
+ int rr = *in_row++;
+ int gg = *in_row++;
+ int bb = *in_row++;
+ int aa = *in_row++;
+ if (aa == 0) {
+ // Zero out the RGB channels when transparent.
+ rr = gg = bb = 0;
+ }
+ out_row[x * bpp] = rr;
+ out_row[x * bpp + 1] = gg;
+ out_row[x * bpp + 2] = bb;
+ if (bpp == 4) {
+ out_row[x * bpp + 3] = aa;
+ }
+ }
+ png_write_row(write_ptr, out_row.get());
+ }
+ } else {
+ // The source image can be used as-is, just tell libpng whether or not to
+ // ignore the alpha channel.
+ if (new_color_type == PNG_COLOR_TYPE_RGB) {
+ // Delete the extraneous alpha values that we appended to our buffer
+ // when reading the original values.
+ png_set_filler(write_ptr, 0, PNG_FILLER_AFTER);
+ }
+ png_write_image(write_ptr, image->rows.get());
+ }
+ } else {
+ LOG(FATAL) << "unreachable";
+ }
+
+ png_write_end(write_ptr, write_info_ptr);
+ return true;
+}
+
+} // namespace android