Skip to main content

Image

The Image group contains a file/stream matrix for two operations: re-encoding an image at a requested compression setting and proportionally fitting it inside a requested width/height box. Current implementations recognise JPEG and PNG rather than acting as general-purpose image converters.

Choosing an entry​

  • Choose CompressImage... when dimensions must remain unchanged and the source should be decoded and re-encoded.
  • Choose ResizeImage... when the image must fit proportionally within a bounding box.
  • Select the FileToFile, FileToStream, StreamToFile or StreamToStream form according to where the bytes currently live and who owns the destination.

Representative entries include CompressImageFileToStream, ResizeImageFileToFile and ResizeImageStreamToStream. The sidebar contains the complete generated matrix.

Format selection and dimensions​

File-source operations detect the supported source format. Stream-source operations inspect data at the stream's current position. For resized file destinations, the destination extension can select JPEG or PNG; stream destinations generally preserve the source format. Read the exact child page before assuming that renaming an extension converts a format or that compression has the same meaning for JPEG and PNG.

Resize dimensions describe a maximum box, not independent forced dimensions. The scale is the smaller of requested-width/source-width and requested-height/source-height, so the image can be upscaled when both requested limits are larger. Zero, negative, extreme and overflow-prone dimensions are unsafe inputs; validate limits before allocating or decoding.

Compression has format-specific rules. JPEG quality is assigned directly to the valid 1..100 range and re-encoding is lossy. PNG remains lossless, but Velox's current mapping makes compression level 0 unreachable and maps every input of 90 or greater to level 10; the installed PNG component accepts only 0..9, so range-checked product builds raise ERangeError. Treat that as a current product defect, not a useful maximum-quality setting.

Ownership, effects and resource limits​

Streams passed by the script remain caller/Velox-owned. Image procedures can read from the current source position and replace or append destination content according to the selected implementation; callers must establish and then inspect the documented positions. Do not free a stream supplied by Velox.

File destinations are external side effects and can be created or replaced before a later mapping failure. Source images can be hostile or unexpectedly large: compressed byte size does not bound decoded pixel memory. Restrict file size, pixel dimensions, format and destination path before processing untrusted input.

These pages are based on product-source analysis. No image operation or image-function test bed has been run as part of this documentation workflow.