SkSurface::MakeRasterN32Premul always returns 0 pointer

[扈马克]

Hi all,

I'm a beginner with Skia. Writing my first program, I have the following code to create a SkSurface:

sk_sp<SkSurface> rasterSurface = SkSurface::MakeRasterN32Premul( imageWidth, imageHeight );
SkCanvas* rasterCanvas = rasterSurface->getCanvas();
.....

Unfortunately, rasterSurface always is a 0 pointer. Doing a bit of debugging, I find that in

SkSurfaceValidateRasterInfo(const SkImageInfo& info, size_t rowBytes), SkSurface_Raster.cpp:38, there is a switch depending on SkImageInfo.colorType(). It is  kRGBA_8888_SkColorType and the program goes to the default-switch, returning false.

Is something in my code wrong or could it be that there is something wrong with my compilation (since kN32_SkColorType is assigned to a different value with a preprocessor if in SkImageInfo.h:82)?

If it is the compilation, I'm on kubuntu 17.04 and I'm using the following commands for checkout and compilation:

git clone 'https://chromium.googlesource.com/chromium/tools/depot_tools.git'
export PATH="${PWD}/depot_tools:${PATH}"
git clone https://skia.googlesource.com/skia.git
cd skia
python tools/git-sync-deps
bin/gn gen out/Shared --args='is_official_build=true is_component_build=true extra_cflags_cc=["-Wno-error"]'
ninja -C out/Shared

Thank you for any help/hints,
Marco

[Mike Reed]

kN32 can be either RGBA or BGRA. If your system is defining it to be BGRA, then surface creation will fail.

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[扈马克]

I see. Is this related to big endian vs. little endian or how does the system define it?
If it is endian, I'm using a normal intel 64bit pc (little endian).

Thanks,
Marco

Am Freitag, 16. Juni 2017 15:13:04 UTC+2 schrieb Mike Reed:

kN32 can be either RGBA or BGRA. If your system is defining it to be BGRA, then surface creation will fail.

On Fri, Jun 16, 2017 at 9:02 AM, 扈马克 <geoh...@gmail.com> wrote:

Hi all,

I'm a beginner with Skia. Writing my first program, I have the following code to create a SkSurface:

sk_sp<SkSurface> rasterSurface = SkSurface::MakeRasterN32Premul( imageWidth, imageHeight );
SkCanvas* rasterCanvas = rasterSurface->getCanvas();
.....

Unfortunately, rasterSurface always is a 0 pointer. Doing a bit of debugging, I find that in

SkSurfaceValidateRasterInfo(const SkImageInfo& info, size_t rowBytes), SkSurface_Raster.cpp:38, there is a switch depending on SkImageInfo.colorType(). It is  kRGBA_8888_SkColorType and the program goes to the default-switch, returning false.

Is something in my code wrong or could it be that there is something wrong with my compilation (since kN32_SkColorType is assigned to a different value with a preprocessor if in SkImageInfo.h:82)?

If it is the compilation, I'm on kubuntu 17.04 and I'm using the following commands for checkout and compilation:

git clone 'https://chromium.googlesource.com/chromium/tools/depot_tools.git'
export PATH="${PWD}/depot_tools:${PATH}"
git clone https://skia.googlesource.com/skia.git
cd skia
python tools/git-sync-deps
bin/gn gen out/Shared --args='is_official_build=true is_component_build=true extra_cflags_cc=["-Wno-error"]'
ninja -C out/Shared

Thank you for any help/hints,
Marco

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[扈马克]

I now edited SkImageInfo such that kN32_SkColorType = kRGBA_8888_SkColorType.
Now it works perfectly! So it seems that the endianness was somehow not correctly detected on my system (and also on my intel notbook with kubuntu 16.10).

Marco

[Brian Osman]

It sounds like something else may be wrong, actually. kN32 can be either RGBA or BGRA, but it needs to be consistently defined for all .cpp files. I see that you're building Skia as a static library (and then trying to use the library like you posted). Can you try adding #include <SkTypes.h> before you include any other Skia headers (in your own code). I suspect that kN32 is defaulting to something different in your code (from what it's set to in Skia).

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[扈马克]

I'm building skia as a dynamic library. Unfortunately, including SkTypes before the other headers does not solve the problem

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[Hal Canary]

The simplest explanation is that you built Skia with different setting than you have in your headers when compiled your client code..

Try this:

    sk_sp<SkSurface> s;
    SkColorType ct;

    ct = kRGBA_8888_SkColorType;

    s = SkSurface::MakeRaster(SkImageInfo::Make(width, height, ct, kPremul_SkAlphaType));

    if (s) { printf("kRGBA_8888_SkColorType works!\n"); }

    ct = kBGRA_8888_SkColorType;

    s = SkSurface::MakeRaster(SkImageInfo::Make(width, height, ct, kPremul_SkAlphaType));

    if (s) { printf("kBGRA_8888_SkColorType works!\n"); }

[扈马克]

Ah, didn't know about the longer version of SkSurface::MakeRaster. kBGRA_8888_SkColorType works for me, so I'm going to use that instead of modifying SkImageInfo.

Thanks for the help,
Marco

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