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We were numerically overflowing our 16bit coordinates that we communicate

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between these two procs. The fixes was in two parts:

1. Just don't draw bitmaps larger than 64K-1 in width or height, since we
   can't represent those coordinates in our transport format (yet).
2. Perform an unsigned shift during the calculation, so we don't get
   sign-extension bleed when packing the two values (X,Y) into our 32bit
   slot.
Review URL: https://codereview.appspot.com/6173046

git-svn-id: http://skia.googlecode.com/svn/trunk@3836 2bbb7eff-a529-9590-31e7-b0007b416f81
This commit is contained in:
reed@google.com 2012-05-03 20:14:26 +00:00
parent 7265e72555
commit 99c114e0ac
4 changed files with 129 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
include/core/SkShader.h
View File

@ -285,10 +285,15 @@ public:
// Factory methods for stock shaders
/** Call this to create a new shader that will draw with the specified bitmap.
@param src The bitmap to use inside the shader
@param tmx The tiling mode to use when sampling the bitmap in the x-direction.
@param tmy The tiling mode to use when sampling the bitmap in the y-direction.
@return Returns a new shader object. Note: this function never returns null.
*
* If the bitmap cannot be used (e.g. has no pixels, or its dimensions
* exceed implementation limits (currently at 64K - 1)) then SkEmptyShader
* may be returned.
*
* @param src The bitmap to use inside the shader
* @param tmx The tiling mode to use when sampling the bitmap in the x-direction.
* @param tmy The tiling mode to use when sampling the bitmap in the y-direction.
* @return Returns a new shader object. Note: this function never returns null.
*/
static SkShader* CreateBitmapShader(const SkBitmap& src,
TileMode tmx, TileMode tmy);

12
src/core/SkBitmapProcShader.cpp
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@ -271,12 +271,22 @@ static bool canUseColorShader(const SkBitmap& bm, SkColor* color) {
#include "SkTemplatesPriv.h"
static bool bitmapIsTooBig(const SkBitmap& bm) {
// SkBitmapProcShader stores bitmap coordinates in a 16bit buffer, as it
// communicates between its matrix-proc and its sampler-proc. Until we can
// widen that, we have to reject bitmaps that are larger.
//
const int maxSize = 65535;
return bm.width() > maxSize || bm.height() > maxSize;
}
SkShader* SkShader::CreateBitmapShader(const SkBitmap& src,
TileMode tmx, TileMode tmy,
void* storage, size_t storageSize) {
SkShader* shader;
SkColor color;
if (src.isNull()) {
if (src.isNull() || bitmapIsTooBig(src)) {
SK_PLACEMENT_NEW(shader, SkEmptyShader, storage, storageSize);
}
else if (canUseColorShader(src, &color)) {

19
src/core/SkBitmapProcState_matrixProcs.cpp
View File

@ -9,6 +9,13 @@
#include "SkShader.h"
#include "SkUtils.h"
// Helper to ensure that when we shift down, we do it w/o sign-extension
// so the caller doesn't have to manually mask off the top 16 bits
//
static unsigned SK_USHIFT16(unsigned x) {
return x >> 16;
}
/* returns 0...(n-1) given any x (positive or negative).
As an example, if n (which is always positive) is 5...
@ -32,8 +39,8 @@ void decal_nofilter_scale(uint32_t dst[], SkFixed fx, SkFixed dx, int count);
void decal_filter_scale(uint32_t dst[], SkFixed fx, SkFixed dx, int count);
#define MAKENAME(suffix) ClampX_ClampY ## suffix
#define TILEX_PROCF(fx, max) SkClampMax((fx) >> 16, max)
#define TILEY_PROCF(fy, max) SkClampMax((fy) >> 16, max)
#define TILEX_PROCF(fx, max) SkClampMax(SK_USHIFT16(fx), max)
#define TILEY_PROCF(fy, max) SkClampMax(SK_USHIFT16(fy), max)
#define TILEX_LOW_BITS(fx, max) (((fx) >> 12) & 0xF)
#define TILEY_LOW_BITS(fy, max) (((fy) >> 12) & 0xF)
#define CHECK_FOR_DECAL
@ -44,8 +51,8 @@ void decal_filter_scale(uint32_t dst[], SkFixed fx, SkFixed dx, int count);
#endif
#define MAKENAME(suffix) RepeatX_RepeatY ## suffix
#define TILEX_PROCF(fx, max) (((fx) & 0xFFFF) * ((max) + 1) >> 16)
#define TILEY_PROCF(fy, max) (((fy) & 0xFFFF) * ((max) + 1) >> 16)
#define TILEX_PROCF(fx, max) SK_USHIFT16(((fx) & 0xFFFF) * ((max) + 1))
#define TILEY_PROCF(fy, max) SK_USHIFT16(((fy) & 0xFFFF) * ((max) + 1))
#define TILEX_LOW_BITS(fx, max) ((((fx) & 0xFFFF) * ((max) + 1) >> 12) & 0xF)
#define TILEY_LOW_BITS(fy, max) ((((fy) & 0xFFFF) * ((max) + 1) >> 12) & 0xF)
#if defined(__ARM_HAVE_NEON)
@ -63,8 +70,8 @@ void decal_filter_scale(uint32_t dst[], SkFixed fx, SkFixed dx, int count);
#define PREAMBLE_PARAM_Y , SkBitmapProcState::FixedTileProc tileProcY, SkBitmapProcState::FixedTileLowBitsProc tileLowBitsProcY
#define PREAMBLE_ARG_X , tileProcX, tileLowBitsProcX
#define PREAMBLE_ARG_Y , tileProcY, tileLowBitsProcY
#define TILEX_PROCF(fx, max) (tileProcX(fx) * ((max) + 1) >> 16)
#define TILEY_PROCF(fy, max) (tileProcY(fy) * ((max) + 1) >> 16)
#define TILEX_PROCF(fx, max) SK_USHIFT16(tileProcX(fx) * ((max) + 1))
#define TILEY_PROCF(fy, max) SK_USHIFT16(tileProcY(fy) * ((max) + 1))
#define TILEX_LOW_BITS(fx, max) tileLowBitsProcX(fx, (max) + 1)
#define TILEY_LOW_BITS(fy, max) tileLowBitsProcY(fy, (max) + 1)
#include "SkBitmapProcState_matrix.h"

96
tests/DrawBitmapRectTest.cpp
View File

@ -8,6 +8,101 @@
#include "Test.h"
#include "SkBitmap.h"
#include "SkCanvas.h"
#include "SkShader.h"
static void assert_ifDrawnTo(skiatest::Reporter* reporter,
const SkBitmap& bm, bool shouldBeDrawn) {
for (int y = 0; y < bm.height(); ++y) {
for (int x = 0; x < bm.width(); ++x) {
if (shouldBeDrawn) {
if (0 == *bm.getAddr32(x, y)) {
REPORTER_ASSERT(reporter, false);
return;
}
} else {
// should not be drawn
if (*bm.getAddr32(x, y)) {
REPORTER_ASSERT(reporter, false);
return;
}
}
}
}
}
static void test_wacky_bitmapshader(skiatest::Reporter* reporter,
int width, int height, bool shouldBeDrawn) {
SkBitmap dev;
dev.setConfig(SkBitmap::kARGB_8888_Config, 0x56F, 0x4f6);
dev.allocPixels();
dev.eraseColor(0); // necessary, so we know if we draw to it
SkMatrix matrix;
SkCanvas c(dev);
matrix.setAll(-119.34097, -43.436558, 93489.945,
43.436558, -119.34097, 123.98426,
0, 0, 1);
c.concat(matrix);
SkBitmap bm;
bm.setConfig(SkBitmap::kARGB_8888_Config, width, height);
bm.allocPixels();
bm.eraseColor(SK_ColorRED);
SkShader* s = SkShader::CreateBitmapShader(bm, SkShader::kRepeat_TileMode,
SkShader::kRepeat_TileMode);
matrix.setAll(0.0078740157, 0, 249,
0, 0.0078740157, 239,
0, 0, 1);
s->setLocalMatrix(matrix);
SkPaint paint;
paint.setShader(s)->unref();
SkRect r = SkRect::MakeXYWH(681, 239, 695, 253);
c.drawRect(r, paint);
assert_ifDrawnTo(reporter, dev, shouldBeDrawn);
}
/*
* Original bug was asserting that the matrix-proc had generated a (Y) value
* that was out of range. This led (in the release build) to the sampler-proc
* reading memory out-of-bounds of the original bitmap.
*
* We were numerically overflowing our 16bit coordinates that we communicate
* between these two procs. The fixes was in two parts:
*
* 1. Just don't draw bitmaps larger than 64K-1 in width or height, since we
* can't represent those coordinates in our transport format (yet).
* 2. Perform an unsigned shift during the calculation, so we don't get
* sign-extension bleed when packing the two values (X,Y) into our 32bit
* slot.
*
* This tests exercises the original setup, plus 3 more to ensure that we can,
* in fact, handle bitmaps at 64K-1 (assuming we don't exceed the total
* memory allocation limit).
*/
static void test_giantrepeat_crbug118018(skiatest::Reporter* reporter) {
static const struct {
int fWidth;
int fHeight;
bool fExpectedToDraw;
} gTests[] = {
{ 0x1b294, 0x7f, false }, // crbug 118018 (width exceeds 64K)
{ 0xFFFF, 0x7f, true }, // should draw, test max width
{ 0x7f, 0xFFFF, true }, // should draw, test max height
{ 0xFFFF, 0xFFFF, false }, // allocation fails (too much RAM)
};
for (size_t i = 0; i < SK_ARRAY_COUNT(gTests); ++i) {
test_wacky_bitmapshader(reporter,
gTests[i].fWidth, gTests[i].fHeight,
gTests[i].fExpectedToDraw);
}
}
///////////////////////////////////////////////////////////////////////////////
static void test_nan_antihair(skiatest::Reporter* reporter) {
SkBitmap bm;
@ -72,6 +167,7 @@ static void TestDrawBitmapRect(skiatest::Reporter* reporter) {
REPORTER_ASSERT(reporter, check_for_all_zeros(dst));
test_nan_antihair(reporter);
test_giantrepeat_crbug118018(reporter);
}
#include "TestClassDef.h"