ARGB image encoder for checksums.

src/utils/SkBitmapTransformer.h

-
-/*
- * Copyright 2012 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkBitmapTransformer_DEFINED
-#define SkBitmapTransformer_DEFINED
-
-#include "SkBitmap.h"
-
-/**
- * Class that can copy pixel data out of an SkBitmap, transforming it
- * into the appropriate PixelFormat.
- *
- * As noted in https://codereview.appspot.com/6849119/#msg6 and
- * https://codereview.appspot.com/6900047 , at some point we might want
- * to make this more general purpose:
- * - support more PixelFormats
- * - use existing SkCanvas::Config8888 enum instead of new PixelFormat enum
- * - add method to copy pixel data for a single row, instead of the whole bitmap
- * - add methods to copy pixel data INTO an SkBitmap
- *
- * That would allow us to replace SkCopyConfig8888ToBitmap() in
- * src/core/SkConfig8888.h , as well as the transformations used by
- * src/images/SkImageDecoder_libpng.cpp , with this common code.
- *
- * But for now, we want something more narrowly targeted, just
- * supplying what is needed by SkBitmapChecksummer.
- */
-class SkBitmapTransformer {
-public:
-    enum PixelFormat {
-        // 32 bits per pixel, ARGB byte order, with the alpha-channel
-        // value premultiplied into the R/G/B channel values.
-        kARGB_8888_Premul_PixelFormat,
-
-        // marks the end of the list
-        kLast_PixelFormat = kARGB_8888_Premul_PixelFormat,
-    };
-
-    /**
-     * Creates an SkBitmapTransformer instance that can transform between
-     * the given bitmap and a pixel buffer with given pixelFormat.
-     *
-     * Call IsValid() before using, to confirm that this particular
-     * bitmap/pixelFormat combination is supported!
-     */
-    SkBitmapTransformer(const SkBitmap& bitmap, PixelFormat pixelFormat) :
-        fBitmap(bitmap), fPixelFormat(pixelFormat) {}
-
-    /**
-     * Returns true iff we can convert between fBitmap and fPixelFormat.
-     * If this returns false, the return values of any other methods will
-     * be meaningless!
-     *
-     * @param logReason whether to log the reason why this combination
-     *                  is unsupported (only applies in debug mode)
-     */
-    bool isValid(bool logReason=false) const;
-
-    /**
-     * Returns the number of bytes needed to store a single row of the
-     * bitmap's pixels if converted to pixelFormat.
-     */
-    size_t bytesNeededPerRow() const {
-        // This is hard-coded for the single supported PixelFormat.
-        return fBitmap.width() * 4;
-    }
-
-    /**
-     * Returns the number of bytes needed to store the entire bitmap
-     * if converted to pixelFormat, ASSUMING that it is written
-     * out as a single contiguous blob of pixels (no leftover bytes
-     * at the end of each row).
-     */
-    size_t bytesNeededTotal() const {
-        return this->bytesNeededPerRow() * fBitmap.height();
-    }
-
-    /**
-     * Writes the entire bitmap into dstBuffer, using the already-specified
-     * pixelFormat. Returns true if successful.
-     *
-     * dstBufferSize is the maximum allowable bytes to write into dstBuffer;
-     * if that is not large enough to hold the entire bitmap, then this
-     * will fail immediately and return false.
-     * We force the caller to pass this in to avoid buffer overruns in
-     * unanticipated cases.
-     *
-     * All pixels for all rows will be written into dstBuffer as a
-     * single contiguous blob (no skipped pixels at the end of each
-     * row).
-     */
-    bool copyBitmapToPixelBuffer (void *dstBuffer, size_t dstBufferSize) const;
-
-private:
-    const SkBitmap& fBitmap;
-    const PixelFormat fPixelFormat;
-};
-
-#endif