SkJpegCodec

src/codec/SkJpegDecoderMgr.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkJpegDecoderMgr.h"
+#include "SkJpegUtility.h"
+
+/*
+ * Print information, warning, and error messages
+ */
+static void print_message(const j_common_ptr info, const char caller[]) {
+    char buffer[JMSG_LENGTH_MAX];
+    info->err->format_message(info, buffer);
+    SkCodecPrintf("libjpeg error %d <%s> from %s\n", info->err->msg_code, buffer, caller);
+}
+
+/*
+ * Reporting functions for libjpeg
+ */
+static void emit_message(j_common_ptr info, int) {
+    print_message(info, "emit_message");
+}
+static void output_message(j_common_ptr info) {
+    print_message(info, "output_message");
+}
+
+/*
+ * Choose the size of the memory buffer on Android
+ */
+static void overwrite_mem_buffer_size(jpeg_decompress_struct* fDInfo) {
+#ifdef SK_BUILD_FOR_ANDROID
+
+// Use 30 MB for devices with a large amount of system memory and 5MB otherwise
+// TODO: (msarett) This matches SkImageDecoder.  Why were these values chosen?
+#ifdef ANDROID_LARGE_MEMORY_DEVICE
+    fDInfo.mem->max_memory_to_use = 30 * 1024 * 1024;
+#else
+    fDInfo.mem->max_memory_to_use = 5 * 1024 * 1024;
+#endif
+
+#endif // SK_BUILD_FOR_ANDROID
+}
+
+bool JpegDecoderMgr::returnFalse(const char caller[]) {
+    print_message((j_common_ptr) &fDInfo, caller);
+    return false;
+}
+
+SkCodec::Result JpegDecoderMgr::returnFailure(const char caller[], SkCodec::Result result) {
+    print_message((j_common_ptr) &fDInfo, caller);
+    return result;
+}
+
+SkColorType JpegDecoderMgr::getColorType() {
+    switch (fDInfo.jpeg_color_space) {
+        case JCS_CMYK:
+        case JCS_YCCK:
+            // libjpeg cannot convert from CMYK or YCCK to RGB.
+            // Here, we ask libjpeg to give us CMYK samples back and
+            // we will later manually convert them to RGB.
+            fDInfo.out_color_space = JCS_CMYK;
+            return kN32_SkColorType;
+        case JCS_GRAYSCALE:
+            fDInfo.out_color_space = JCS_GRAYSCALE;
+            return kGray_8_SkColorType;
+        default:
+#ifdef ANDROID_RGB
+            fDInfo.out_color_space = JCS_RGBA_8888;
+#else
+            fDInfo.out_color_space = JCS_RGB;
+#endif
+            return kN32_SkColorType;
+    }
+}
+
+JpegDecoderMgr::JpegDecoderMgr(SkStream* stream)
+    : fSrcMgr(stream)
+{
+    // Error manager must be set before any calls to libjeg in order to handle failures
+    fDInfo.err = jpeg_std_error(&fErrorMgr);
+    fErrorMgr.error_exit = skjpeg_err_exit;
+}
+
+void JpegDecoderMgr::init() {
+    jpeg_create_decompress(&fDInfo);
+    fDInfo.src = &fSrcMgr;
+    overwrite_mem_buffer_size(&fDInfo);
+    fDInfo.err->emit_message = &emit_message;
+    fDInfo.err->output_message = &output_message;
+}
+
+JpegDecoderMgr::~JpegDecoderMgr() {
+    jpeg_destroy_decompress(&fDInfo);

[scroggo, 2015/04/15 00:31:06]

Don't we only want to do this if init was called?

[msarett, 2015/04/15 12:43:11]

Yes it is unnecessary otherwise!  Fixed.

+}
+
+jpeg_decompress_struct* JpegDecoderMgr::dinfo() {
+    return &fDInfo;
+}
+
+skjpeg_error_mgr* JpegDecoderMgr::errorMgr() {

[scroggo, 2015/04/15 00:31:06]

You appear to only use this to get the jump buffer. I think you could instead
just have a method which returns that?

[msarett, 2015/04/15 12:43:12]

I had exactly the same though.

I wrote:

jmp_buf getJmpBuf() { return fErrorMgr.fJmpBuf; }

The compiler complains about this because the function returns an array, so I
wrote:

jmp_buf* getJmpBuf() { return &fErrorMgr.fJmpBuf; }

Then to use it I wrote:

*fDecoderMgr->getJmpBuf()

Then I didn't like how this looked and I got rid of it.  However, given that we
had the same thought, I think this is worth doing.

The new version returns a reference, which I think is a good solution.

+    return &fErrorMgr;
+}