LIBJXL
|
Decoding API for JPEG XL. More...
#include <stddef.h>
#include <stdint.h>
#include "jxl/codestream_header.h"
#include "jxl/color_encoding.h"
#include "jxl/jxl_export.h"
#include "jxl/memory_manager.h"
#include "jxl/parallel_runner.h"
#include "jxl/types.h"
Go to the source code of this file.
Typedefs | |
typedef struct JxlDecoderStruct | JxlDecoder |
typedef void(* | JxlImageOutCallback) (void *opaque, size_t x, size_t y, size_t num_pixels, const void *pixels) |
Enumerations | |
enum | JxlSignature { JXL_SIG_NOT_ENOUGH_BYTES = 0, JXL_SIG_INVALID = 1, JXL_SIG_CODESTREAM = 2, JXL_SIG_CONTAINER = 3 } |
enum | JxlDecoderStatus { JXL_DEC_SUCCESS = 0, JXL_DEC_ERROR = 1, JXL_DEC_NEED_MORE_INPUT = 2, JXL_DEC_NEED_PREVIEW_OUT_BUFFER = 3, JXL_DEC_NEED_DC_OUT_BUFFER = 4, JXL_DEC_NEED_IMAGE_OUT_BUFFER = 5, JXL_DEC_JPEG_NEED_MORE_OUTPUT = 6, JXL_DEC_BASIC_INFO = 0x40, JXL_DEC_EXTENSIONS = 0x80, JXL_DEC_COLOR_ENCODING = 0x100, JXL_DEC_PREVIEW_IMAGE = 0x200, JXL_DEC_FRAME = 0x400, JXL_DEC_DC_IMAGE = 0x800, JXL_DEC_FULL_IMAGE = 0x1000, JXL_DEC_JPEG_RECONSTRUCTION = 0x2000 } |
enum | JxlColorProfileTarget { JXL_COLOR_PROFILE_TARGET_ORIGINAL = 0, JXL_COLOR_PROFILE_TARGET_DATA = 1 } |
Decoding API for JPEG XL.
typedef struct JxlDecoderStruct JxlDecoder |
Opaque structure that holds the JPEGXL decoder.
Allocated and initialized with JxlDecoderCreate(). Cleaned up and deallocated with JxlDecoderDestroy().
typedef void(* JxlImageOutCallback) (void *opaque, size_t x, size_t y, size_t num_pixels, const void *pixels) |
Callback function type for JxlDecoderSetImageOutCallback.
The callback bay be called simultaneously by different threads when using a threaded parallel runner, on different pixels.
opaque | optional user data, as given to JxlDecoderSetImageOutCallback. |
x | horizontal position of leftmost pixel of the pixel data. |
y | vertical position of the pixel data. |
num_pixels | amount of pixels included in the pixel data, horizontally. This is not the same as xsize of the full image, it may be smaller. |
pixels | pixel data as a horizontal stripe, in the format passed to JxlDecoderSetImageOutCallback. The memory is not owned by the user, and is only valid during the time the callback is running. |
Defines which color profile to get: the profile from the codestream metadata header, which represents the color profile of the original image, or the color profile from the pixel data received by the decoder. Both are the same if the basic has uses_original_profile set.
Enumerator | |
---|---|
JXL_COLOR_PROFILE_TARGET_ORIGINAL | Get the color profile of the original image from the metadata.. |
JXL_COLOR_PROFILE_TARGET_DATA | Get the color profile of the pixel data the decoder outputs. |
enum JxlDecoderStatus |
Return value for JxlDecoderProcessInput. The values above 0x40 are optional informal events that can be subscribed to, they are never returned if they have not been registered with JxlDecoderSubscribeEvents.
enum JxlSignature |
The result of JxlSignatureCheck.
JXL_EXPORT JxlDecoder* JxlDecoderCreate | ( | const JxlMemoryManager * | memory_manager | ) |
Creates an instance of JxlDecoder and initializes it.
memory_manager
will be used for all the library dynamic allocations made from this instance. The parameter may be NULL, in which case the default allocator will be used. See jpegxl/memory_manager.h for details.
memory_manager | custom allocator function. It may be NULL. The memory manager will be copied internally. |
NULL
if the instance can not be allocated or initialized JXL_EXPORT JXL_DEPRECATED JxlDecoderStatus JxlDecoderDCOutBufferSize | ( | const JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
size_t * | size | ||
) |
Returns the minimum size in bytes of the DC image output buffer for the given format. This is the buffer for JxlDecoderSetDCOutBuffer. Requires the basic image information is available in the decoder.
dec | decoder object |
format | format of pixels |
size | output value, buffer size in bytes |
DEPRECATED: the DC feature in this form will be removed. You can use JxlDecoderFlushImage for progressive rendering.
JXL_EXPORT JxlDecoderStatus JxlDecoderDefaultPixelFormat | ( | const JxlDecoder * | dec, |
JxlPixelFormat * | format | ||
) |
Get the default pixel format for this decoder.
Requires that the decoder can produce JxlBasicInfo.
dec | JxlDecoder to query when creating the recommended pixel format. |
format | JxlPixelFormat to populate with the recommended settings for the data loaded into this decoder. |
JXL_EXPORT void JxlDecoderDestroy | ( | JxlDecoder * | dec | ) |
Deinitializes and frees JxlDecoder instance.
dec | instance to be cleaned up and deallocated. |
JXL_EXPORT JxlDecoderStatus JxlDecoderFlushImage | ( | JxlDecoder * | dec | ) |
Outputs progressive step towards the decoded image so far when only partial input was received. If the flush was successful, the buffer set with JxlDecoderSetImageOutBuffer will contain partial image data.
Can be called when JxlDecoderProcessInput returns JXL_DEC_NEED_MORE_INPUT, after the JXL_DEC_FRAME event already occurred and before the JXL_DEC_FULL_IMAGE event occurred for a frame.
dec | decoder object |
JXL_EXPORT JxlDecoderStatus JxlDecoderGetBasicInfo | ( | const JxlDecoder * | dec, |
JxlBasicInfo * | info | ||
) |
Outputs the basic image information, such as image dimensions, bit depth and all other JxlBasicInfo fields, if available.
dec | decoder object |
info | struct to copy the information into, or NULL to only check whether the information is available through the return value. |
JXL_EXPORT JxlDecoderStatus JxlDecoderGetColorAsEncodedProfile | ( | const JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
JxlColorProfileTarget | target, | ||
JxlColorEncoding * | color_encoding | ||
) |
Outputs the color profile as JPEG XL encoded structured data, if available. This is an alternative to an ICC Profile, which can represent a more limited amount of color spaces, but represents them exactly through enum values.
It is often possible to use JxlDecoderGetColorAsICCProfile as an alternative anyway. The following scenarios are possible:
If you wish to render the image using a system that supports ICC profiles, use JxlDecoderGetColorAsICCProfile first. If you're looking for a specific color space possibly indicated in the JPEG XL image, use JxlDecoderGetColorAsEncodedProfile first.
dec | decoder object |
format | pixel format to output the data to. Only used for JXL_COLOR_PROFILE_TARGET_DATA, may be nullptr otherwise. |
target | whether to get the original color profile from the metadata or the color profile of the decoded pixels. |
color_encoding | struct to copy the information into, or NULL to only check whether the information is available through the return value. |
JXL_EXPORT JxlDecoderStatus JxlDecoderGetColorAsICCProfile | ( | const JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
JxlColorProfileTarget | target, | ||
uint8_t * | icc_profile, | ||
size_t | size | ||
) |
Outputs ICC profile if available. The profile is only available if JxlDecoderGetICCProfileSize returns success. The output buffer must have at least as many bytes as given by JxlDecoderGetICCProfileSize.
dec | decoder object |
format | pixel format to output the data to. Only used for JXL_COLOR_PROFILE_TARGET_DATA, may be nullptr otherwise. |
target | whether to get the original color profile from the metadata or the color profile of the decoded pixels. |
icc_profile | buffer to copy the ICC profile into |
size | size of the icc_profile buffer in bytes |
JXL_EXPORT JxlDecoderStatus JxlDecoderGetExtraChannelInfo | ( | const JxlDecoder * | dec, |
size_t | index, | ||
JxlExtraChannelInfo * | info | ||
) |
Outputs information for extra channel at the given index. The index must be smaller than num_extra_channels in the associated JxlBasicInfo.
dec | decoder object |
index | index of the extra channel to query. |
info | struct to copy the information into, or NULL to only check whether the information is available through the return value. |
JXL_EXPORT JxlDecoderStatus JxlDecoderGetExtraChannelName | ( | const JxlDecoder * | dec, |
size_t | index, | ||
char * | name, | ||
size_t | size | ||
) |
Outputs name for extra channel at the given index in UTF-8. The index must be smaller than num_extra_channels in the associated JxlBasicInfo. The buffer for name must have at least name_length + 1 bytes allocated, gotten from the associated JxlExtraChannelInfo.
dec | decoder object |
index | index of the extra channel to query. |
name | buffer to copy the name into |
size | size of the name buffer in bytes |
JXL_EXPORT JxlDecoderStatus JxlDecoderGetFrameHeader | ( | const JxlDecoder * | dec, |
JxlFrameHeader * | header | ||
) |
Outputs the information from the frame, such as duration when have_animation. This function can be called when JXL_DEC_FRAME occurred for the current frame, even when have_animation in the JxlBasicInfo is JXL_FALSE.
dec | decoder object |
header | struct to copy the information into, or NULL to only check whether the information is available through the return value. |
JXL_EXPORT JxlDecoderStatus JxlDecoderGetFrameName | ( | const JxlDecoder * | dec, |
char * | name, | ||
size_t | size | ||
) |
Outputs name for the current frame. The buffer for name must have at least name_length + 1 bytes allocated, gotten from the associated JxlFrameHeader.
dec | decoder object |
name | buffer to copy the name into |
size | size of the name buffer in bytes, including zero termination character, so this must be at least JxlFrameHeader.name_length + 1. |
JXL_EXPORT JxlDecoderStatus JxlDecoderGetICCProfileSize | ( | const JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
JxlColorProfileTarget | target, | ||
size_t * | size | ||
) |
Outputs the size in bytes of the ICC profile returned by JxlDecoderGetColorAsICCProfile, if available, or indicates there is none available. In most cases, the image will have an ICC profile available, but if it does not, JxlDecoderGetColorAsEncodedProfile must be used instead.
dec | decoder object |
format | pixel format to output the data to. Only used for JXL_COLOR_PROFILE_TARGET_DATA, may be nullptr otherwise. |
target | whether to get the original color profile from the metadata or the color profile of the decoded pixels. |
size | variable to output the size into, or NULL to only check the return status. |
JXL_EXPORT JxlDecoderStatus JxlDecoderImageOutBufferSize | ( | const JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
size_t * | size | ||
) |
Returns the minimum size in bytes of the image output pixel buffer for the given format. This is the buffer for JxlDecoderSetImageOutBuffer. Requires the basic image information is available in the decoder.
dec | decoder object |
format | format of the pixels. |
size | output value, buffer size in bytes |
JXL_EXPORT JxlDecoderStatus JxlDecoderPreviewOutBufferSize | ( | const JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
size_t * | size | ||
) |
Returns the minimum size in bytes of the preview image output pixel buffer for the given format. This is the buffer for JxlDecoderSetPreviewOutBuffer. Requires the preview header information is available in the decoder.
dec | decoder object |
format | format of pixels |
size | output value, buffer size in bytes |
JXL_EXPORT JxlDecoderStatus JxlDecoderProcessInput | ( | JxlDecoder * | dec | ) |
Decodes JPEG XL file using the available bytes. Requires input has been set with JxlDecoderSetInput. After JxlDecoderProcessInput, input can optionally be released with JxlDecoderReleaseInput and then set again to next bytes in the stream. JxlDecoderReleaseInput returns how many bytes are not yet processed, before a next call to JxlDecoderProcessInput all unprocessed bytes must be provided again (the address need not match, but the contents must), and more bytes may be concatenated after the unprocessed bytes.
The returned status indicates whether the decoder needs more input bytes, or more output buffer for a certain type of output data. No matter what the returned status is (other than JXL_DEC_ERROR), new information, such as JxlDecoderGetBasicInfo, may have become available after this call. When the return value is not JXL_DEC_ERROR or JXL_DEC_SUCCESS, the decoding requires more JxlDecoderProcessInput calls to continue.
dec | decoder object |
JXL_EXPORT size_t JxlDecoderReleaseInput | ( | JxlDecoder * | dec | ) |
Releases input which was provided with JxlDecoderSetInput. Between JxlDecoderProcessInput and JxlDecoderReleaseInput, the user may not alter the data in the buffer. Calling JxlDecoderReleaseInput is required whenever any input is already set and new input needs to be added with JxlDecoderSetInput, but is not required before JxlDecoderDestroy or JxlDecoderReset. Calling JxlDecoderReleaseInput when no input is set is not an error and returns 0.
dec | decoder object |
JXL_EXPORT size_t JxlDecoderReleaseJPEGBuffer | ( | JxlDecoder * | dec | ) |
Releases buffer which was provided with JxlDecoderSetJPEGBuffer.
Calling JxlDecoderReleaseJPEGBuffer is required whenever a buffer is already set and a new buffer needs to be added with JxlDecoderSetJPEGBuffer, but is not required before JxlDecoderDestroy or JxlDecoderReset.
Calling JxlDecoderReleaseJPEGBuffer when no input is set is not an error and returns 0.
dec | decoder object |
JXL_EXPORT void JxlDecoderReset | ( | JxlDecoder * | dec | ) |
Re-initializes a JxlDecoder instance, so it can be re-used for decoding another image. All state and settings are reset as if the object was newly created with JxlDecoderCreate, but the memory manager is kept.
dec | instance to be re-initialized. |
JXL_EXPORT void JxlDecoderRewind | ( | JxlDecoder * | dec | ) |
Rewinds decoder to the beginning. The same input must be given again from the beginning of the file and the decoder will emit events from the beginning again. When rewinding (as opposed to JxlDecoderReset), the decoder can keep state about the image, which it can use to skip to a requested frame more efficiently with JxlDecoderSkipFrames. After rewind, JxlDecoderSubscribeEvents can be used again, and it is feasible to leave out events that were already handled before, such as JXL_DEC_BASIC_INFO and JXL_DEC_COLOR_ENCODING, since they will provide the same information as before.
dec | decoder object |
JXL_EXPORT JXL_DEPRECATED JxlDecoderStatus JxlDecoderSetDCOutBuffer | ( | JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
void * | buffer, | ||
size_t | size | ||
) |
Sets the buffer to write the lower resolution (8x8 sub-sampled) DC image to. The size of the buffer must be at least as large as given by JxlDecoderDCOutBufferSize. The buffer follows the format described by JxlPixelFormat. The DC image has dimensions ceil(xsize / 8) * ceil(ysize / 8). The buffer is owned by the caller.
dec | decoder object |
format | format of pixels. Object owned by user and its contents are copied internally. |
buffer | buffer type to output the pixel data to |
size | size of buffer in bytes |
DEPRECATED: the DC feature in this form will be removed. You can use JxlDecoderFlushImage for progressive rendering.
JXL_EXPORT JxlDecoderStatus JxlDecoderSetImageOutBuffer | ( | JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
void * | buffer, | ||
size_t | size | ||
) |
Sets the buffer to write the full resolution image to. This can be set when the JXL_DEC_FRAME event occurs, must be set when the JXL_DEC_NEED_IMAGE_OUT_BUFFER event occurs, and applies only for the current frame. The size of the buffer must be at least as large as given by JxlDecoderImageOutBufferSize. The buffer follows the format described by JxlPixelFormat. The buffer is owned by the caller.
dec | decoder object |
format | format of the pixels. Object owned by user and its contents are copied internally. |
buffer | buffer type to output the pixel data to |
size | size of buffer in bytes |
JXL_EXPORT JxlDecoderStatus JxlDecoderSetImageOutCallback | ( | JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
JxlImageOutCallback | callback, | ||
void * | opaque | ||
) |
Sets pixel output callback. This is an alternative to JxlDecoderSetImageOutBuffer. This can be set when the JXL_DEC_FRAME event occurs, must be set when the JXL_DEC_NEED_IMAGE_OUT_BUFFER event occurs, and applies only for the current frame. Only one of JxlDecoderSetImageOutBuffer or JxlDecoderSetImageOutCallback may be used for the same frame, not both at the same time.
The callback will be called multiple times, to receive the image data in small chunks. The callback receives a horizontal stripe of pixel data, 1 pixel high, xsize pixels wide, called a scanline. The xsize here is not the same as the full image width, the scanline may be a partial section, and xsize may differ between calls. The user can then process and/or copy the partial scanline to an image buffer. The callback bay be called simultaneously by different threads when using a threaded parallel runner, on different pixels.
If JxlDecoderFlushImage is not used, then each pixel will be visited exactly once by the different callback calls, during processing with one or more JxlDecoderProcessInput calls. These pixels are decoded to full detail, they are not part of a lower resolution or lower quality progressive pass, but the final pass.
If JxlDecoderFlushImage is used, then in addition each pixel will be visited zero or one times during the blocking JxlDecoderFlushImage call. Pixels visited as a result of JxlDecoderFlushImage may represent a lower resolution or lower quality intermediate progressive pass of the image. Any visited pixel will be of a quality at least as good or better than previous visits of this pixel. A pixel may be visited zero times if it cannot be decoded yet or if it was already decoded to full precision (this behavior is not guaranteed).
dec | decoder object |
format | format of the pixels. Object owned by user and its contents are copied internally. |
callback | the callback function receiving partial scanlines of pixel data. |
opaque | optional user data, which will be passed on to the callback, may be NULL. |
JXL_EXPORT JxlDecoderStatus JxlDecoderSetInput | ( | JxlDecoder * | dec, |
const uint8_t * | data, | ||
size_t | size | ||
) |
Sets input data for JxlDecoderProcessInput. The data is owned by the caller and may be used by the decoder until JxlDecoderReleaseInput is called or the decoder is destroyed or reset so must be kept alive until then.
dec | decoder object |
data | pointer to next bytes to read from |
size | amount of bytes available starting from data |
JXL_EXPORT JxlDecoderStatus JxlDecoderSetJPEGBuffer | ( | JxlDecoder * | dec, |
uint8_t * | data, | ||
size_t | size | ||
) |
Sets output buffer for reconstructed JPEG codestream.
The data is owned by the caller and may be used by the decoder until JxlDecoderReleaseJPEGBuffer is called or the decoder is destroyed or reset so must be kept alive until then.
dec | decoder object |
data | pointer to next bytes to write to |
size | amount of bytes available starting from data |
JXL_EXPORT JxlDecoderStatus JxlDecoderSetKeepOrientation | ( | JxlDecoder * | dec, |
JXL_BOOL | keep_orientation | ||
) |
Enables or disables preserving of original orientation. Some images are encoded with an orientation tag indicating the image is rotated and/or mirrored (here called the original orientation).
*) If keep_orientation is JXL_FALSE (the default): the decoder will perform work to undo the transformation. This ensures the decoded pixels will not be rotated or mirrored. The decoder will always set the orientation field of the JxlBasicInfo to JXL_ORIENT_IDENTITY to match the returned pixel data. The decoder may also swap xsize and ysize in the JxlBasicInfo compared to the values inside of the codestream, to correctly match the decoded pixel data, e.g. when a 90 degree rotation was performed.
*) If this option is JXL_TRUE: then the image is returned as-is, which may be rotated or mirrored, and the user must check the orientation field in JxlBasicInfo after decoding to correctly interpret the decoded pixel data. This may be faster to decode since the decoder doesn't have to apply the transformation, but can cause wrong display of the image if the orientation tag is not correctly taken into account by the user.
By default, this option is disabled, and the decoder automatically corrects the orientation.
This function must be called at the beginning, before decoding is performed.
dec | decoder object |
keep_orientation | JXL_TRUE to enable, JXL_FALSE to disable. |
JXL_EXPORT JxlDecoderStatus JxlDecoderSetParallelRunner | ( | JxlDecoder * | dec, |
JxlParallelRunner | parallel_runner, | ||
void * | parallel_runner_opaque | ||
) |
Set the parallel runner for multithreading. May only be set before starting decoding.
dec | decoder object |
parallel_runner | function pointer to runner for multithreading. It may be NULL to use the default, single-threaded, runner. A multithreaded runner should be set to reach fast performance. |
parallel_runner_opaque | opaque pointer for parallel_runner. |
JXL_EXPORT JxlDecoderStatus JxlDecoderSetPreferredColorProfile | ( | JxlDecoder * | dec, |
const JxlColorEncoding * | color_encoding | ||
) |
Sets the color profile to use for JXL_COLOR_PROFILE_TARGET_DATA for the special case when the decoder has a choice. This only has effect for a JXL image where uses_original_profile is false, and the original color profile is encoded as an ICC color profile rather than a JxlColorEncoding with known enum values. In most other cases (uses uses_original_profile is true, or the color profile is already given as a JxlColorEncoding), this setting is ignored and the decoder uses a profile related to the image. No matter what, the JXL_COLOR_PROFILE_TARGET_DATA must still be queried to know the actual data format of the decoded pixels after decoding.
The intended use case of this function is for cases where you are using a color management system to parse the original ICC color profile (JXL_COLOR_PROFILE_TARGET_ORIGINAL), from this you know that the ICC profile represents one of the color profiles supported by JxlColorEncoding (such as sRGB, PQ or HLG): in that case it is beneficial (but not necessary) to use JxlDecoderSetPreferredColorProfile to match the parsed profile. The JXL decoder has no color management system built in, but can convert XYB color to any of the ones supported by JxlColorEncoding.
Can only be set after the JXL_DEC_COLOR_ENCODING event occurred and before any other event occurred, and can affect the result of JXL_COLOR_PROFILE_TARGET_DATA (but not of JXL_COLOR_PROFILE_TARGET_ORIGINAL), so should be used after getting JXL_COLOR_PROFILE_TARGET_ORIGINAL but before getting JXL_COLOR_PROFILE_TARGET_DATA. The color_encoding must be grayscale if num_color_channels from the basic info is 1, RGB if num_color_channels from the basic info is 3.
If JxlDecoderSetPreferredColorProfile is not used, then for images for which uses_original_profile is false and with ICC color profile, the decoder will choose linear sRGB for color images, linear grayscale for grayscale images. This function only sets a preference, since for other images the decoder has no choice what color profile to use, it is determined by the image.
dec | decoder object |
color_encoding | the default color encoding to set |
JXL_EXPORT JxlDecoderStatus JxlDecoderSetPreviewOutBuffer | ( | JxlDecoder * | dec, |
const JxlPixelFormat * | format, | ||
void * | buffer, | ||
size_t | size | ||
) |
Sets the buffer to write the small resolution preview image to. The size of the buffer must be at least as large as given by JxlDecoderPreviewOutBufferSize. The buffer follows the format described by JxlPixelFormat. The preview image dimensions are given by the JxlPreviewHeader. The buffer is owned by the caller.
dec | decoder object |
format | format of pixels. Object owned by user and its contents are copied internally. |
buffer | buffer type to output the pixel data to |
size | size of buffer in bytes |
JXL_EXPORT size_t JxlDecoderSizeHintBasicInfo | ( | const JxlDecoder * | dec | ) |
Returns a hint indicating how many more bytes the decoder is expected to need to make JxlDecoderGetBasicInfo available after the next JxlDecoderProcessInput call. This is a suggested large enough value for the amount of bytes to provide in the next JxlDecoderSetInput call, but it is not guaranteed to be an upper bound nor a lower bound. Can be used before the first JxlDecoderProcessInput call, and is correct the first time in most cases. If not, JxlDecoderSizeHintBasicInfo can be called again to get an updated hint.
dec | decoder object |
JXL_EXPORT void JxlDecoderSkipFrames | ( | JxlDecoder * | dec, |
size_t | amount | ||
) |
Makes the decoder skip the next amount
frames. It still needs to process the input, but will not output the frame events. It can be more efficient when skipping frames, and even more so when using this after JxlDecoderRewind. If the decoder is already processing a frame (could have emitted JXL_DEC_FRAME but not yet JXL_DEC_FULL_IMAGE), it starts skipping from the next frame. If the amount is larger than the amount of frames remaining in the image, all remaining frames are skipped. Calling this function multiple times adds the amount to skip to the already existing amount. A frame here is defined as a frame that without skipping emits events such as JXL_DEC_FRAME and JXL_FULL_IMAGE, frames that are internal to the file format but are not rendered as part of an animation, or are not the final still frame of a still image, are not counted.
dec | decoder object |
amount | the amount of frames to skip |
JXL_EXPORT JxlDecoderStatus JxlDecoderSubscribeEvents | ( | JxlDecoder * | dec, |
int | events_wanted | ||
) |
Select for which informative events (JXL_DEC_BASIC_INFO, etc...) the decoder should return with a status. It is not required to subscribe to any events, data can still be requested from the decoder as soon as it available. By default, the decoder is subscribed to no events (events_wanted == 0), and the decoder will then only return when it cannot continue because it needs more input data or more output buffer. This function may only be be called before using JxlDecoderProcessInput
dec | decoder object |
events_wanted | bitfield of desired events. |
JXL_EXPORT uint32_t JxlDecoderVersion | ( | void | ) |
Decoder library version.
JXL_EXPORT JxlSignature JxlSignatureCheck | ( | const uint8_t * | buf, |
size_t | len | ||
) |
JPEG XL signature identification.
Checks if the passed buffer contains a valid JPEG XL signature. The passed buf
of size size
doesn't need to be a full image, only the beginning of the file.