Native bindings to stb_image.h from the stb library.

Quick notes

Primarily of interest to game developers and other people who can avoid problematic images and only need the trivial interface. Supported formats:

• JPEG baseline & progressive (12 bpc/arithmetic not supported, same as stock IJG lib
• PNG 1/2/4/8/16-bit-per-channel
• TGA (not sure what subset, if a subset)
• BMP non-1bpp, non-RLE
• PSD (composited view only, no extra channels, 8/16 bit-per-channel)
• GIF (*desired_channels always reports as 4-channel)
• HDR (radiance rgbE format)
• PIC (Softimage PIC)
• PNM (PPM and PGM binary only)

Animated GIF still needs a proper API, but here's one way to do it.

Features:

• decode from memory
• decode from arbitrary I/O callbacks
• SIMD acceleration on x86/x64 (SSE2) and ARM (NEON)

Limitations:

• no 12-bit-per-channel JPEG
• no JPEGs with arithmetic coding
• GIF always returns *channels_in_file=4

Basic usage (see HDR discussion below for HDR usage):

int x,y,n;
unsigned char *data = stbi_load(filename, &x, &y, &n, 0);
// ... process data if not NULL ...
// ... x = width, y = height, n = # 8-bit components per pixel ...
// ... replace '0' with '1'..'4' to force that many components per pixel
// ... but 'n' will always be the number that it would have been if you said 0
stbi_image_free(data)

HDR image support

stb_image supports loading HDR images in general, and currently the Radiance .HDR file format specifically. You can still load any file through the existing interface; if you attempt to load an HDR file, it will be automatically remapped to LDR, assuming gamma 2.2 and an arbitrary scale factor defaulting to 1; both of these constants can be reconfigured through this interface:

stbi_hdr_to_ldr_gamma(2.2f);
stbi_hdr_to_ldr_scale(1.0f);

(note, do not use inverse constants; stbi_image will invert them appropriately).

Additionally, there is a new, parallel interface for loading files as (linear) floats to preserve the full dynamic range:

float *data = stbi_loadf(filename, &x, &y, &n, 0);

If you load LDR images through this interface, those images will be promoted to floating point values, run through the inverse of constants corresponding to the above:

stbi_ldr_to_hdr_scale(1.0f);
stbi_ldr_to_hdr_gamma(2.2f);

Finally, given a filename (or an open file or memory block) containing image data, you can query for the "most appropriate" interface to use (that is, whether the image is HDR or not), using:

stbi_is_hdr(char *filename);

iPhone PNG support

We optionally support converting iPhone-formatted PNGs (which store premultiplied BGRA) back to RGB, even though they're internally encoded differently. To enable this conversion, call convert_iphone_png_to_rgb(1).

Call set_unpremultiply_on_load(1) as well to force a divide per pixel to remove any premultiplied alpha *only* if the image file explicitly says there's premultiplied data (currently only happens in iPhone images, and only if iPhone convert-to-rgb processing is on).