pdfviewer: set backdround to transparent, and add an app to chop transparent content in png files.

experimental/PdfViewer/chop_transparency_main.cpp

Index: experimental/PdfViewer/chop_transparency_main.cpp
===================================================================
--- experimental/PdfViewer/chop_transparency_main.cpp	(revision 0)
+++ experimental/PdfViewer/chop_transparency_main.cpp	(revision 0)
@@ -0,0 +1,176 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkBitmap.h"
+#include "SkColorPriv.h"
+#include "SkCommandLineFlags.h"
+#include "SkData.h"
+#include "SkForceLinking.h"
+#include "SkGraphics.h"
+#include "SkImageDecoder.h"
+#include "SkImageEncoder.h"
+#include "SkOSFile.h"
+#include "SkRandom.h"
+#include "SkStream.h"
+#include "SkTArray.h"
+#include "SkTemplates.h"
+
+__SK_FORCE_IMAGE_DECODER_LINKING;
+
+DEFINE_string2(readPath, r, "", "Folder(s) and files to decode images. Required.");
+
+struct Format {
+    SkImageEncoder::Type    fType;
+    SkImageDecoder::Format  fFormat;
+    const char*             fSuffix;
+};
+
+static const Format gFormats[] = {
+    { SkImageEncoder::kBMP_Type, SkImageDecoder::kBMP_Format, ".bmp" },
+    { SkImageEncoder::kGIF_Type, SkImageDecoder::kGIF_Format, ".gif" },
+    { SkImageEncoder::kICO_Type, SkImageDecoder::kICO_Format, ".ico" },
+    { SkImageEncoder::kJPEG_Type, SkImageDecoder::kJPEG_Format, ".jpg" },
+    { SkImageEncoder::kPNG_Type, SkImageDecoder::kPNG_Format, ".png" },
+    { SkImageEncoder::kWBMP_Type, SkImageDecoder::kWBMP_Format, ".wbmp" },
+    { SkImageEncoder::kWEBP_Type, SkImageDecoder::kWEBP_Format, ".webp" }
+};
+
+SkISize opaqueSize(const SkBitmap& bm) {
+    int width = 1;
+    int height = 1;
+    for (int y = 0 ; y < bm.height(); y++) {
+        for (int x = 0 ; x < bm.height(); x++) {
+            SkColor color = bm.getColor(x, y);
+            if (SkColorGetA(color) != 0) {
+                height = y + 1;
+                width = width > (x + 1) ? width : x + 1;
+            }
+        }
+    }
+
+    return SkISize::Make(width, height);
+}
+
+static void setup_bitmap(SkBitmap* bitmap, int width, int height) {
+    bitmap->setConfig(SkBitmap::kARGB_8888_Config, width, height);
+
+    bitmap->allocPixels();
+}
+
+
+static bool write_bitmap(const char outName[], const SkBitmap& bm) {
+    SkISize size = opaqueSize(bm);
+    SkBitmap dst;
+    setup_bitmap(&dst, size.width(), size.height());
+
+    for (int y = 0 ; y < dst.height(); y++) {
+        for (int x = 0 ; x < dst.width(); x++) {
+            SkColor color = bm.getColor(x, y);
+            if (SkColorGetA(color) != 0xff) {
+                int a = SkColorGetA(color);
+                int r = SkColorGetR(color);
+                int g = SkColorGetG(color);
+                int b = SkColorGetB(color);
+                if (a == 0) {
+                    r = g = b = 0;
+                } else {
+                    r = (r * a) / 255;
+                    g = (g * a) / 255;
+                    b = (b * a) / 255;
+                    a = 255;
+                }
+                color = SkColorSetARGB((U8CPU)a, (U8CPU)r, (U8CPU)g, (U8CPU)b);
+            }
+            *dst.getAddr32(x, y) = color;
+        }
+    }
+
+    return SkImageEncoder::EncodeFile(outName, dst, SkImageEncoder::kPNG_Type, 100);
+}
+
+static void decodeFileAndWrite(const char srcPath[]) {
+    SkBitmap bitmap;
+    SkFILEStream stream(srcPath);
+    if (!stream.isValid()) {
+        return;
+    }
+
+    SkImageDecoder* codec = SkImageDecoder::Factory(&stream);
+    if (NULL == codec) {
+        return;
+    }
+
+    SkAutoTDelete<SkImageDecoder> ad(codec);
+
+    stream.rewind();
+
+    if (!codec->decode(&stream, &bitmap, SkBitmap::kARGB_8888_Config,
+                       SkImageDecoder::kDecodePixels_Mode)) {
+        return;
+    }
+
+    write_bitmap(srcPath, bitmap);
+}
+
+/**
+ *  Return true if the filename represents an image.
+ */
+static bool is_image_file(const char* filename) {
+    const char* gImageExtensions[] = {
+        ".png", ".PNG", ".jpg", ".JPG", ".jpeg", ".JPEG", ".bmp", ".BMP",
+        ".webp", ".WEBP", ".ico", ".ICO", ".wbmp", ".WBMP", ".gif", ".GIF"
+    };
+    for (size_t i = 0; i < SK_ARRAY_COUNT(gImageExtensions); ++i) {
+        if (SkStrEndsWith(filename, gImageExtensions[i])) {
+            return true;
+        }
+    }
+    return false;
+}
+
+int tool_main(int argc, char** argv);
+int tool_main(int argc, char** argv) {
+    SkCommandLineFlags::SetUsage("Decode files, and optionally write the results to files.");
+    SkCommandLineFlags::Parse(argc, argv);
+
+    if (FLAGS_readPath.count() < 1) {
+        SkDebugf("Folder(s) or image(s) to decode are required.\n");
+        return -1;
+    }
+
+
+    SkAutoGraphics ag;
+
+    for (int i = 0; i < FLAGS_readPath.count(); i++) {
+        const char* readPath = FLAGS_readPath[i];
+        if (strlen(readPath) < 1) {
+            break;
+        }
+        if (sk_isdir(readPath)) {
+            const char* dir = readPath;
+            SkOSFile::Iter iter(dir);
+            SkString filename;
+            while (iter.next(&filename)) {
+                if (!is_image_file(filename.c_str())) {
+                    continue;
+                }
+                SkString fullname = SkOSPath::SkPathJoin(dir, filename.c_str());
+                decodeFileAndWrite(fullname.c_str());
+            }
+        } else if (sk_exists(readPath) && is_image_file(readPath)) {
+            decodeFileAndWrite(readPath);
+        }
+    }
+
+    return 0;
+}
+
+#if !defined SK_BUILD_FOR_IOS
+int main(int argc, char * const argv[]) {
+    return tool_main(argc, (char**) argv);
+}
+#endif